梅毒最主要的传播途径是()
A．输血
B．性交经粘膜擦伤处
C．医源性传播
D．接吻
E．衣物传染
参考答案：B
There are so many kinds of MP5 in the shop. We can not decide _____.[ ]
A. what to buy
B. to buy what
C. which to buy
D. to buy which
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