SAT Subject Biology Practice Question 320: Answer and Explanation

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Question: 320

10. 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

Based on the results in Table 2, if a volunteer were to ingest 4.5 g sodium chloride dissolved in 100 ml water, what would be the approximate predicted urine volume collected after one hour?

A. 20 ml
B. 30 ml
C. 40 ml
D. 50 ml
E. 60 ml

Correct Answer: C


C From Table 2, an increase in sodium chloride of 0.9 g results in a decrease in urine volume of approximately 40 ml. When 3.6 g sodium chloride are ingested, 82 ml urine is produced; thus if 4.5 g sodium chloride were to be ingested, the expected urine volume would be 40 ml less, approximately 40 ml.

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