I was about to leave my house________the phone rang. 
#72178
A
while
B
when
C
as
D
after
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We hadn't met for 20 years, but I recognized her_____ I saw her.
#73296
A
the moment
B
for the moment
C
the moment when
D
at the moment when
Gun control is a subject     Americans have argued for a long time. 
#74509
A
of which
B
with which
C
about which
D
into which
The old man has two sons,________is a soldier.
#67015
A
one of whom
B
both of them
C
all of whom
D
both of whom