问题补充:
Some people waste a lot of food others don’t have enough to eat.
A. however
B. when
C. as
D. while
答案:
A. however
B. when
C. as
(答案→)D. while
解析:原句意思是:一些人浪费许多的粮食,而另外一些人却没有足够的东西吃.however“然而”,“但是”,when“当……时”, as“当……时候”,“一边……一边……”, while“而”,“与此同时”,本句里没有主从关系,所以不选B和C,however的转折语气强,此句是并列地说两件事,根据句意,可知选D.