Your mother points out to you a magazine article that says that better nutrition is the reason modern Americans are taller than Americans of two centuries ago. You tell her that
a. while this is true, other factors such as a reduction in infectious diseases also contribute to the increase in height.
b. this is not true, because the obesity epidemic has started to make Americans shorter.
c. the truth is that we are far less healthy than we were when agriculture first began.
d. All of the above