The percentage of peole weighing over 150 pounds is higher

Be aware of "short" questions. They are always more difficult than the longer ones. If you see a short question, do NOT skim. The trap may be hidden in just one word.

This question is "ALSO must be true", not "must be true" question. The difference between the two is the correct answer of the later could be a paraphrase of the stimulus, however, the correct answer of the former cannot be a paraphrase.

ANALYZE THE STIMULUS:

The percentage of people weighing over 150 pounds is higher in Irvine than any other city. However, the percentage of people weighing over 180 pounds is higher in Tustin.

If the statements above are true, which of the following must also be true?

ANALYZE EACH ANSWER:

A) Irvine has the second highest percentage of people weighing over 180 pounds.
Wrong. Clearly out of scope. Eliminate right away.

B) Average weight is higher in Tustin than in Irvine
Wrong. Cannot say that. We do NOT have information about people in other categories (< 150 pounds)

C) Some people in Irvine weigh between 150 and 180 pounds
Correct. This is an "ALSO" must be true answer. Because the stimulus say Irvine has some people weighting more than 150 pounds, and the percentage of people weighting over 180 pounds higher in Tustin (than in Irvine <-- Because the stimulus clearly is comparing Tustin and Irvine). ==> We are 100% sure that Irvine has some people who weight between 150 and 180 pounds

D) The number of people who weigh more than 150 pounds is greater in Irvine than in Tustin.
Wrong. We have ONLY percentage, we CAN'T say anything about absolute value.
For example:
Irvine has 100 people, 20 people weighting over 150 pounds --> percentage = 20%
Tustin has 1000 people, 100 people weighting over 150 pounds --> percentage = 10%
==> Even though the percentage number of Irvine is larger, the absolute value is smaller.

E) The percentage of people who weigh over 180 pounds is greater in Tustin than in Irvine.
Wrong. E is just a paraphrase of the second sentence. It would be correct if the question was "must be true". However, the question stem clearly says "which ALSO must be true". Thus, the answer that only repeats the stimulus is wrong.

Hope it helps.