Because of the great speed of light,we see a lamp light up almost at the exact moment ___ .

题目

Because of the great speed of light,we see a lamp light up almost at the exact moment ___ .
A .We turn it on
B .When we turn on it
C .that we turn on it
D .which we turn it on

答案

选择A.
首先开灯,应该是turn on the light,当light用it指代时,只能是turn it on而不能是turn on it,所以只有A或者D是可能的,然后主句中的the exact moment是时刻,表时间,所以只能用when或者that（除了一些特殊情况,从句中不能用that,一般都可以用that）,因为which是指代人或者物的,所以综合一下只有A是对的.望采纳,还有疑问问哈.