[求助]大全95题

1.        Although some officials noted that using machines for farming in China costs more than traditional hand cultivation, the mechanization of farming in the village of Long Bow doubled the corn yield while the previous year’s costs were cut in half.

(A) mechanization of farming in the village of Long Bow doubled the corn yield while the previous year’s costs were cut in half

(B) mechanization of farming in the village of Long Bow doubled the corn yield while cutting costs to half those of the previous year

(C) mechanization of farming in the village of Long Bow doubled the corn yield as cost were cut to half of the previous year’s

(D) farming mechanization in the village of Long Bow doubled the corn yield as it cut in half the previous year’s costs（B）

(E) farming mechanization in the village of Long Bow doubled the corn yield while costs were cut to half that of the previous year

请问这里的B，while后面是什么成分，是不是一个省略，省略了什么？

谢谢！

不能算省略，习惯用法吧。

while doing = while sth. do

状语从句的省略：

主+谓+状语从句引导词+(主句主语+be)+ v-ing
                         |                                 
                     可以省略吗？
即当这里的be是构成进行时态的助动词时还可以省略吗？