--- Are you sure you have to ? It's been very late. --- I don't know I can do it if not n

问题补充：

--- Are you sure you have to ? Its been very late.

--- I don know I can do it if not now.

A. where

B. why

C. when

D. how

答案：

A. where

B. why

(答案→)C. when

D. how

解析：可联系答.案.网客服索取。