Some people waste a lot of food others haven't enough to eat.A. onceB. whenC. asD. while

问题补充：

Some people waste a lot of food others haven enough to eat.

A. once

B. when

C. as

D. while

答案：

A. once

B. when

C. as

(答案→)D. while

解析：考查连词：A. once一旦B. when当…时候，C. as当…时候，正如，因为，D. while当…时候，虽然，然而，句意：一些人浪费粮食而有些人吃不饱。选D。