---John, why are you so upset? ---I­­­      my cell phone all morning but it is nowhere to be found.
#101303
A
am looking for
B
have looked for
C
have been looking for
D
had looked for
推荐题目
When you don’t know a word, you can _________ in the dictionary. 
#99231
A
look it up
B
set it up
C
give it up
D
pick it up
They _____ on the program for almost one week before I joined them, and now we _____ it as no good results have come out.
#101978
A
had been working; are still working
B
had worked; were still working
C
have been working; have worked
D
have worked; are still working
Experiments of this kind ___in both the U.S and Europe well before the Second World War
#100340
A
had conducted
B
have conducted
C
have been conducted
D
had been conducted