A、  B、  C、  C以when开头进行提问时，应该回答“时间”，所以(C)是正确答案。(A)branch office意为“分公司，分店”，但此题和场所没关系。(B)because用来回答以why开头的提问，和本题不符合

(Woman) Who ordered a new computer for the office?
(Man) (A) Mr. Sanchez did.
(B) Tomorrow.
(C) Yes, a new computer.

(Woman) When did they fill the assistant manager position?
(Man) (A) At the new branch office.
(B) Because he retired.
(C) Last Monday.