Perhaps the day will come ____ people will be able to breathe clean air in cities．
#32785
A
when
B
while
C
as
D
since
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The most important thing about my job is ______ I help protect ordinary people from the volcano.
#31632
A
how
B
that
C
what
D
不填
I felt I was so happy ______ it was the first time that I had gone to the Universal Studio.
#30958
A
that
B
even though
C
as
D
when
Please remind me _______ he said he was going. I may be in time to see him off.
#33619
A
where
B
when
C
how
D
what