Question

Diuretics are substances that help eliminate water from the body. Few volunteers were taken into the study, all of which had same mass. 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

Volunteer	Amount caffeine ingested (in 100 ml water)	Volume urine collected after 1 hour
A	50 mg	302 ml
B	100 mg	492 ml
C	150 mg	667 ml
D	200 mg	863 ml

Table-2

Volunteer	Amount sodium chloride ingested (in 100 ml water)	Volume urine collected after 1 hour
A	0.9 g	201 ml
B	1.8 g	162 ml
C	2.7 g	125 ml
D	3.6 g	82 ml

Table-3

Volunteer	Volume water ingested	Volume urine collected after 1 hour
A	100 ml	230 ml
B	200 ml	240 ml
C	300 ml	252 ml
D	400 ml	263 ml

The reason of ingesting the plain water was to

• A. Rehydrate the volunteers
• B. Dissolve the substances
• C. Act as a control
• D. Flush out the kidneys
• E. Act as a positive test substance

Answer 1

The correct option is C Act as a control

Because the caffeine and the sodium chloride were dissolved in water, plain water was consumed as a control to make sure the effects seen were due to the added substances and not the water. Thus, the correct answer is option C.