Please remind your grandpa to take medicine on time, for a man of his age be very forgetful．
A. need
B. must
C. shall
D. can
网友回答
A. need
B. must
C. shall
(答案→)D. can
解析：考查情态动词。Need需要；must 必须；shall 将会；can可能。句意：请提醒你的祖父按时吃药，对于他这个年龄的人来说可能会比较健忘。Can表理论上的可能性。选D。