问题补充:
--Where have you all day?
--- I came back at noon and I in this office since then.
A. been in; had been
B. been in; was
C. been; have been
D. been; am
答案:
A. been in; had been
B. been in; was
(答案→)C. been; have been
D. been; am
解析:句意:你整天都在哪里?我在中午回来了,自从那时后就一直呆在办公室里。句中有since句中用现在完成时,故选C