So fast _________ that it is difficult for us to imagine its spe

So fast _________ that it is difficult for us to imagine its speed.
A、light travel
B、travels the light
C、do light travel
D、does light travel
【正确答案】：D
【题目解析】：这是英语的一种语法---“倒装句”； 是指将谓语的一部分如助动词或情态倒装至主语之前。如果句中的谓语没有助动词或情态动词，则需添助动词do, does或did其置于主语之前。 这句话的原来句形是： Light travels so fast that it is difficult for us to imagine its speed. 为了强调so fast, 使用了倒装句。