Scientists formerly believed that the rocky planetsEarth, Mercury,

2. Which of the following best describes the “observation” (line 6) referred to in the passage?

A. The rocky planets were created by the rapid gravitational collapse of a dust cloud.
B. Certain features on the Moon’s surface are impact craters caused by collisions with objects such as planetesimals.- Correct
C. The rocky planets were formed by a slow accretion of cosmic dust into increasingly larger bodies.
D. The number of objects colliding with the Moon appears to have been high for a while and then rapidly diminished.
E. Tere are far fewer planetesimals in existence today than there were about 4.5 billion years ago.

1. Option A.

Explanation: First sentence says- Scientists formerly believed that the rocky planets—Earth, Mercury, Venus, and Mars—were created by the rapid gravitational collapse of a dust cloud, a deflation giving rise to a dense orb. so it indicates a fast process.
On the other hand Schimdt's theory says,
"Schmidt’s 1944 theory of accretion. According to this theory, cosmic dust gradually lumped into" so its a slow process.

Stem II is wrong, because the first theory does not provide any explanation to what caused the craters while Schimdt's theory does. No ground of disagreement whatsoever.


Stem III is wrong because, both theories mention cosmic dusts and dust clouds , but none of them particularly recognizes it in any way. All they care about is How the planets are formed, not what constitute those.


2. Option D.

We need to rephrase the bold part in the given sentence: That view was challenged in the 1960s when studies of Moon craters revealed that these craters were caused by the impact of objects that were in great abundance about 4.5 billion years ago but whose number appeared to have quickly decreased shortly thereafter.

Sajjad1994 , In 2nd question , Option B is very well inferred from the passage that "Certain features on the Moon’s surface are impact craters caused by collisions with objects such as planetesimals" and Option D : Told about the collision by objects as well as the object where available before and then diminished.

so in such type of question where you we need to best describe the role of a particular word , here it is "observation" , here we always need to select answer choice which is word to word match with the passage (like in option D) ? and please provide a reason for elimination of choice B.

Option B is incorrect because it specifically refers to features on the Moon's surface being impact craters caused by collisions with objects such as planetesimals. While it is true that the passage mentions Moon craters being caused by the impact of objects, the observation discussed in the passage is not limited to the Moon's surface features. The broader observation is about the general decrease in the number of objects colliding with the Moon over time, and this observation led to a reevaluation of the formation of rocky planets.

 
­You are right! Fixed now.

My issue with Choice D of question 2 is that it says "been high for a while and then rapidly diminished". But the passage says that "objects were in great abundance 4.5 billion years ago but whose numbers appeared to have quickly diminished shortly thereafter". The contrast between "for a while" and "shortly thereafter" led me to pass on this option. GMATNinja Bunuel KarishmaB any thoughts on this?