A、  B、  C、  B因为是以When开头的疑问句，所以在回答的时候要包括时间、日期、钟点等内容。所以正确答案是(B)。(A)用来回答以Why开头的问句，而(C)则用来回答以Where开始的问句。

I’ve really enjoyed this project.
(A)When did she sign up?
(B)It starts next week.
(C)The rest of us have too.

When will the new billing period begin?
(A)Because we lost an invoice.
(B)In about two weeks.
(C)Around the front plaza.