To see if baldness is caused by a high protein diet, a scientist gives
one group of men a low protein diet and another group of men a high
protein diet. What is the independent variable in this experiment?
A. the amount of protein in the diets of the men
B. whether or not the men develop baldness
C. the age of the men and the amount of water they are given to drink
D. the number of men in each group
