Among the many concerns that gardeners must address is to decide

Question

Among the many concerns that gardeners must address is to decide whether the land they wish to cultivate is suitable for the types of plants they wish to grow. This means checking the soil’s pH, a measure of how acid or alkaline a substance is. Soil’s pH is important because it explains how difficult it will be for plants to take nutrients from the soil. Plant roots absorb the nutrients they need—such as iron and nitrogen—when those nutrients are dissolved in water. If the soil solution (the mixture of water and nutrients in the soil) is too acid or alkaline, some nutrients won’t dissolve easily, so they won’t be available for uptake by roots.

While seed manufacturers will often suggest a good pH range for their plants, the truth is that most plants will tolerate a far wider range in pH than what is suggested. Most nutrients that plants need can dissolve easily when the pH of the soil solution ranges from 6.0 to 7.5. Below pH 6.0, some nutrients, such as nitrogen, phosphorus, and potassium, are less available. When pH exceeds 7.5, iron, manganese, and phosphorus are less available.

Soil pH is affected by many factors, including the amount of local rainfall and the temperature range in the area. In the Pacific Northwest and the Eastern United States, where rainfall is heavy, the soil tends to be moderately acidic. In the Midwest, soil tends to be neutral. In the western United States, especially in areas of frequent drought, soil tends to be alkaline. Of course, soils that have been cultivated are often quite different than the naturally occurring soil in any region. During construction of homes and other buildings, topsoil is frequently removed and may be replaced by a different type of soil.    1 
 1. The first sentence in the third paragraph is meant to

A. provide a comparison of soil pH levels for readers to use based on their location
B. give a general overview of the range of soil pH levels in the United States
C. present soil pH as a fixed measurement that can be learned 
D. introduce the idea of soil pH
E. explain that the rest of the paragraph will give advice on what kind of plants to grow in various areas

2 
 2. Based on the passage, the author would agree with all of the following statements EXCEPT:

A. Soil pH is a shifting and unpredictable quality.
B. Understanding the soil pH of his garden will help the gardener grow more robust plants.
C. Soil pH levels vary widely within the United States.
D. Seed manufacturers are careful to give clear instructions on the best soil pH for their plants, and their directives must be followed.
E. Soil pH helps explain why plants can or cannot take in nutrients.

3 
 3. The author’s main purpose in this passage is to

A. provide growing advice for gardeners based on where in the United States they live
B. give an overview of soil pH levels and make a case for how understanding them can improve a gardener’s yield 
C. review best gardening practices
D. demonstrate how to calculate soil pH
E. explain how to test for soil pH

4 
 4. According to the passage, what factors might affect a soil’s pH?

A. Wind and temperature
B. Rainfall and temperature
C. Rainfall and wind
D. Topsoil and alkalinity
E. Alkalinity and acidity

LearningTheRopes · Answer

Can you please explain the reasoning behind question 1?

The question asks about the purpose of the  first sentence  of the third paragraph. While I agree that the third paragraph "give(s) a general overview of the range of soil pH levels in the United States", the first sentence does not.

The first sentence, "Soil pH is affected by many factors, including the amount of local rainfall and the temperature range in the area," does not specifically mention the United States. The sentence is a general statement about factors affecting soil pH.

Are we sure that the question is not referring to the entire 3rd paragraph?

Sajjad1994 · Answer

You probably want to answer the question by reading only and only first sentence of the third paragraph, but this is not the case. You must read the whole passage as it is written. While answering the question you are usually supposed to read the literature in the previous paragraphs and you know what you are reading. What kind of passage it is what it is about and what the topic is overall. So mentioning of United States did not matter in my honest opinion.

LearningTheRopes · Answer

Thanks,

In my opinion, the idea that the sentence "Soil pH is affected by many factors, including the amount of local rainfall and the temperature range in the area" alone gives a " general overview  of the  range  of soil pH levels in the United States" is unfounded. It doesn't say anything about the  range  of soil pH levels. You definitely have to take into account the entire passage, but in my opinion that does not change anything in this case.

The only way this would work is if local rainfall and temperature were defined in previous paragraphs as contributing to a range of soil pH levels in the United States. The first sentence of the third paragraph does not give the general overview. Rather, the entire third paragraph provides the general overview.

Its_me_aka_ak · Answer

even i agree to this. A seems to be a better answer the sentence and passage in question uses US as an example only. sentence mentions itself that the main point is the difference in PH according to climatic conditions in general.

parthwagh · Answer

Here are the answers explained in detail:
 
Main Point:  The passage discusses the importance of soil pH for gardeners, how it affects nutrient availability for plants, and how various factors can influence the pH levels of soil in different regions.

Tone of Author:   Neutral  - The author presents factual information about soil pH and its implications for gardening without expressing personal opinions or emotions.

Paragraph Summaries:
1. Importance of soil pH for nutrient uptake in plants.
2. Tolerance of plants to a range of pH and availability of nutrients at different pH levels.
3. Factors affecting soil pH, including rainfall, temperature, and human activities like construction.

Analysis of Questions:

1. The correct answer is B : give a general overview of the range of soil pH levels in the United States. The first sentence in the third paragraph introduces the topic of regional differences in soil pH across the United States. This sentence is not a comparison (A), does not present pH as a fixed measurement (C), is not introducing the concept of soil pH (D), and does not provide advice on what plants to grow (E).

2. The correct answer is D:  Seed manufacturers are careful to give clear instructions on the best soil pH for their plants, and their directives must be followed. The passage suggests that while seed manufacturers provide a good pH range, most plants will tolerate a wider range than what is suggested, which implies that the directives do not need to be strictly followed. The other statements are supported by the passage, making D the only statement the author would not agree with.

3. The correct answer is B:  give an overview of soil pH levels and make a case for how understanding them can improve a gardener’s yield. The passage discusses how soil pH affects plant nutrient uptake and how understanding this can help gardeners. It does not provide growing advice based on location (A), review general gardening practices (C), demonstrate how to calculate soil pH (D), or explain how to test for soil pH (E).

4. The correct answer is B:  Rainfall and temperature. The passage specifically mentions that rainfall and temperature range in the area affect soil pH. It does not mention wind (A and C) as a factor, nor does it discuss the impact of topsoil and alkalinity (D), or alkalinity and acidity (E) as direct factors affecting soil pH.

karanbishti · Answer

In question 2 why not the answer is A as it mentions unpredictable and it is nowhere in the passage mentioned that it is unpredictable quantity

Sajjad1994 · Answer

A is incorrect because the author does not explicitly state that soil pH is a shifting and unpredictable quality. Instead, he or she highlights that soil pH is affected by various factors, including local rainfall and temperature, but it doesn't characterize it as unpredictable.

MS61 · Answer

1. The first sentence in the third paragraph is meant to

A. provide a comparison of soil pH levels for readers to use based on their location -  No such comparison is mentioned in the paragraph 
B. give a general overview of the range of soil pH levels in the United States -  correct answer. 
C. present soil pH as a fixed measurement that can be learned -  Not mentioned 
D. introduce the idea of soil pH -  Introduction is given in earlier paragraphs ( 1st ) 
E. explain that the rest of the paragraph will give advice on what kind of plants to grow in various areas -  No such advice given.

I eliminated the answers and based on that B was most suitable answer for me.

siddhantvarma · Answer

@ Sajjad1994  If you're saying that the author doesn't explicitly state that soil pH is a shifting and unpredictable quality and doesn't characterize it as unpredictable, shouldn't the answer be A here? The question asks us " Based on the passage, the author would agree with all of the following statements EXCEPT " which means we need to find a statement author would disagree with.

@ GMATNinja  @ KarishmaB  Can you please help me understand how option A is incorrect in Question 2.

glagad · Answer

@ siddhantvarma  - I am going to try and answer this.

What Sajjad meant is - while the author doesn't say it explicitly, he implies that Soil's pH is unpredictable, based on the passage that the soil's pH is affected by many factors out there.

IMO, Soil's pH is unpredictable because the author mentions that its affected by weather conditions like rainfall and temperature and hence Author is likely to agree with it.

However, honestly, when I first read it, it seemed like an option that Author would likely not agree, I kept it for review and came back to it.
Check Option D - the latter part of the sentence - "and their directives must be followed." has been negated by the author explicitly and hence that statement in totality wouldn't be agreed by the author.

Given this, I went back to A and I realised that option D is more correct.

Hope that helps

siddhantvarma · Answer

Thanks for helping out, it makes sense. D is a better choice in that regard, you're right. I'm still not fully convinced if that's the way GMAT passage answer choices are going to be. There's some ambiguity concerning how we can eliminate A. I believe  McGraw Hill  is not a good source for GMAT RC passages.

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Among the many concerns that gardeners must address is to decide

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Among the many concerns that gardeners must address is to decide

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