SAT Subject Biology Practice Question 317: Answer and Explanation

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Question: 317

7. Diuretics are substances that help eliminate water from the body. The effects of various substances were tested on several volunteers. All volunteers had a mass of 70 kg. They drank nothing for eight hours before the test and urinated just prior to ingesting the test substance. The three substances (water, caffeine, and salt) were tested on three separate days. The results are shown in the tables below.

Table 1

Table 2

Table 3

Which of the following substances could be classified as a diuretic?

I. Caffeine

II. Sodium

III. Water

A. I only
B. II only
C. I and II only
D. II and III only
E. I, II, and III

Correct Answer: A


A Diuretics help eliminate water (i.e., increase urine production) from the body. From the data tables, the only substance that increases urine production significantly is caffeine. Don't forget the I, II, III technique here; even just knowing that option I is true allows you to eliminate two (choices B and D) of the five choices.

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