Taking a sweater, it's cold out there.
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He bought two____ (box) of chocolate at the store.
Friendship falls apart because of lack of opportunity___________.
A. to meet.
B. to hang out.
C. to connect.
D. All of the above.
People go to big cities for ______________.
A. Jobs.
B. Opportunities.
C. Peace.
D. A and B.
结构中含有四个手性中心的药物是：
A. 阿莫西林
B. 青霉素
C. 头孢羟氨苄
D. 头孢克洛
E. 头孢噻肟钠
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