There is never enough time to do everything, ______ there is always enough time to do the most important thing. 
#30797
A
and
B
but
C
or
D
so
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 _________ many times, but he still couldn’t understand it.
#32413
A
Having been told
B
Though he had been told
C
He was told
D
Having told
No one knows exactly ______ this important discovery was made.
#33284
A
that   
B
that how   
C
what   
D
when