— Bob has gone to California.— Oh, can you tell me when he ______? 
#102361
A
has left
B
left
C
is leaving
D
would leaving
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All possible means ___ been tried to stop the air______.
#103381
A
has, polluted
B
have, polluting
C
have, being polluted
D
has, being polluted
I'm sorry. I _____________ you__________ to me.
#104802
A
don't know; are speaking
B
don't know ;were speaking
C
didn't know; were speaking
D
didn't know; are speaking
With the rise of modern communication tools, handwritten letters ______ by emails. 
#100623
A
will replace
B
have replaced
C
are replaced
D
are being replaced