Plants _________carbon dioxide and at the same time _________oxygen. So we may put some in our bedrooms to purify the air. 
#65276
A
take in, give out
B
take up, give off
C
take over, give in
D
take off, give up
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After a second thought, Bill ________ a better idea of how to solve the problem.
#65658
A
put up with
B
kept up with
C
came up with
D
mixed up with
His sister left home in 1998, and _______since. 
#84460
A
had not been heard of
B
has not been heard of
C
had not heard of
D
has not heard of