---When did it start?-.A. Two days agoB. For three daysC. A weekD. Two days

问题补充：

---When did it start? ---.

A. Two days ago

B. For three days

C. A week

D. Two days

答案：

(答案→)A. Two days ago

B. For three days

C. A week

D. Two days

解析：根据题干When did it start?可知询问什么时候开始的，表示的是过去的时间，有选择项的提示可知选择A。