Concept:Old age in humans is marked by physical changes such as greying of hair and reduced body functions.
Explanation:Grey hair starts appearing as we grow old.
Mental alertness generally declines, not increases, with old age.
Broadening of the chest occurs during adolescence, not old age.
Attraction to the opposite sex is a change that begins during adolescence.
Therefore, the correct change normally occurring during old age is greying of hair.
Answer:A. Grey hair starts appearing