As he（ ）up since 4 a.m. , he is, no doubt, very tired now.
A、
is
B、
was
C、
has been
D、
had been
【正确答案】：C
【题目解析】：
因为句子中有since，且为自从的含义，所以主句用完成时，从句用一般过去时，选C。句意：由于他从凌晨4点起就起床了，毫无疑问，他现在很累了。
As he（ ）up since 4 a.m. , he is, no doubt, very tired now.
As he（ ）up since 4 a.m. , he is, no doubt, very tired now.
is
was
has been
had been
因为句子中有since，且为自从的含义，所以主句用完成时，从句用一般过去时，选C。句意：由于他从凌晨4点起就起床了，毫无疑问，他现在很累了。