If you feel tired and sick of fat food, that is ______ you have to go to the hospital for medical examination.
#73982
A
why
B
whether
C
when
D
what
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On returning from work, _____.  
#70204
A
John found a letter in the mailbox
B
a letter was found in the mailbox  
C
a letter was in the mailbox
D
the mailbox had a letter in it
Only when       possible to settle the problem.
#67697
A
our teacher comes will it be
B
does our teacher comes will it be
C
our teacher comes it will be
D
has our teacher come will it be