Which of These Is One Reason Why Middle-Aged Women Have

Which of these is one reason why middle-aged women have higher rates of illness than men in the same age group?

A) Women have been underrepresented as participants in medical research trials.
B) There simply are more middle-aged women than men living.
C) Because women have less muscular strength than men,they tend to get sick more often.
D) Because women have weaker immune systems than men.