5 mins 21 secs & got 3 out of 4 correct. A long passage which is tiring to read but pretty straightforward questions.
Summary/Gist:
The passage begins with presenting the downside (cancer-causing chemical formed) of using chlorine to kill bacteria. The entire first paragraph talks about the need for alternate filtration methods as traditional ones lead to chlorine, lead and bacterial problems in water. The next paragraph is a large one which talks about many filtration methods but always gives drawbacks to each. This is a detail question nightmare. The last paragraph introduces a final solution (KDF system) which is a new technique.
Flow of information question made difficult by the tricky options.1. Which of the following best describes the organization of the passage?A. Several methods are described and ranked in terms of desirability.
There is no ranking and hence discarded.B. A general theory is offered and refuted by several counterexamples.
No theory is offered let alone refuted by counterexamples. Discard.C. A current process is assailed, and several alternatives are presented as possible replacements.
Looks suspect. Hold. Fits the bill - several alternatives to filtration are presented and all are possible replacements. This does not capture the entire picture of the passage but is the best of the lot.D. An old solution is revived as a possible remedy to a new problem.
"Old solution revived" is definitely not the case. Discard.E. A paradox is presented, and several examples are used to reconcile it.
No paradox. Discard.Easy detail question. Pretty straightforward and thank the heavens for that 2. Each of the following is a disadvantage of the ion exchange method of water filtration EXCEPT:A. higher sodium levels in the water
B. damaged pipes
C. unaffected contaminants of an organic nature
D. dangerous copper and zinc contamination
TICK.E. an increase of lead
Tricky question - with so much information and options that require close inspection - such questions definitely test the test-taker for time management.3. According to the passage, which of the following can be inferred about the KDF system?A. It prevents the formation of trihalomethane in the water supply.
Suspect. Hold. The KDF method does not deal with chlorine at all. Seems to be the right answer as the alternative filtration ensures that the original cholrine based filtration will not be used and hence the chemical will not be formed.B. It would work much better if used in concert with a semipermeable membrane.
Speculative - not mentioned and hence cannot be "inferred" from the passage.C. The electrochemical reaction causes most of the copper and zinc that are originally introduced into the water to dissolve.
Speculative - again for the same reasons we need to discard it. It is mentioned that the byproduct is copper and zinc but we do not know how exactly they end up in the water. Cannot be inferred.D. Without the additional ceramic pre-filter, it is no more effective than the combined effect of ion exchange and ultraviolet light.
TRAP - I fell for it considering the time it takes to verify. But on verification, it can be seen that this is not the case. Discard.E. Its ability to remove iron from water is superior to that of ion exchange.
Cannot be inferred. No comparisons made. Discard.KDF ticks all the right boxes and just had a harmless byproduct. If somehow the byproduct was harmful or some of the boxes could not be ticked due to new info - we would be looking out for such things.4. According to the passage, the author’s opinion of the best water filtration system would probably change if which of the following were true?A. If the KDF system is used indefinitely, the levels of copper and zinc that it introduces into the water supply will eventually become toxic.
BINGO - this hits the sweet spot of why KDF would go from the best to useless method real fast.B. All new residential dwellings are fitted with pipes made of durable plastic that lead cannot seep through.
Not related to KDF - some of the other methods would benefit but KDF is not affected.C. Ultraviolet light is one-tenth as expensive as each of the other techniques mentioned.
Unrelated to KDF discard.D. Subsequent studies have revealed that there is no relation between trihalomethane and cancer.
Discard for same reason as above.E. KDF is available only in urban areas with tax bases that withstand the cost of installing such a system.
TRAP - this could be a reason to discard it - but to begin with the scope of the passage is "Municipalties" which are urban governments and this options is not as crystal clear as Option (A). Hence discard.Hope this is helpful.
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Regards,
Gladi
“Do. Or do not. There is no try.” - Yoda (The Empire Strikes Back)