Health problems are closely connected with bad eating habits and a of exercise.A. limitB.

问题补充：

Health problems are closely connected with bad eating habits and a of exercise.

A. limit

B. lack

C. need

D. demand

答案：

A. limit

(答案→)B. lack

C. need

D. demand

解析：lack 意为“缺乏”。根据常识可判断出健康问题与坏的饮食习惯和缺乏锻炼有关。limit意为“限制”；need意为“需要”；demand意为“要求,需求(量),需要”。