与尼曼-匹克病密切相关的酶是（）

A.鞘磷酸脂酶

B.葡萄糖－6－磷酸脱氢酶

C.腺苷酸环化酶

D.葡萄糖脑苷酶

E.丙酮酸激酶

Nowadays people take___ exercise a day as they did in the past because of widely used automobiles.   

A．less than half

B．less than as half as

C．less than half as much

D．half less than