SAT Subject Biology Practice Question 318: Answer and Explanation
8. 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.
Which graph best represents the change in urine volume when ingesting caffeine?
A. img alt="" src="images/Prin_9780307945723_epub_211_r1.jpg"/>
B. img alt="" src="images/Prin_9780307945723_epub_212_r1.jpg"/>
C. img alt="" src="images/Prin_9780307945723_epub_213_r1.jpg"/>
D. img alt="" src="images/Prin_9780307945723_epub_214_r1.jpg"/>
E. img alt="" src="images/Prin_9780307945723_epub_215_r1.jpg"/>
Correct Answer: A
A Again, from the data tables, there is a directly proportional (i.e., linear) relationship between the amount of caffeine ingested and the volume of urine produced. As caffeine consumption increases, so does urine volume. The only graph that shows this relationship is choice A.