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I'll phone you ________ I arrive in London．
A．before
B．after
C．until
D．as soon as
________ we were singing happily, he came in．
A．While
B．After
C．Until
D．Before
I met your brother ______ I was walking in the street.
B．until
C．after
D．while
The student didn't stop talking ________ the teacher came in.
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