光圈大小也决定景深的大小。光圈越大，景深越小；光圈越小，景深越大。
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You reach a point __________ medicine can’t help.
A. where
B. in where
C. in which
D. what
We haven't yet settled the question __________ we are going to spend our summer vacation.
A. what
B. where
C. which
D. in where
He has __________ join the army.
A. applied
B. apply to
C. applied to
D. been applied to
I don't know why you _______________ that crowd.
A. bother with
B. bother at
C. bother to
D. bother on
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