He tried his best to solve the problem, _______ difficult it was.
#67486
A
whatever
B
however
C
whichever
D
wherever
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The clever boy made a hole in the wall, _______ he could see _____ was going on inside house. 
#73752
A
which; what
B
through which; what
C
through that; what
D
what; that
Can you lend me the book ______the other day? 
#73763
A
about which you talked
B
which you talked
C
about that you talked
D
that you talked