实验动物传染病流行的传播途径有直接传染和（）。
A.接触
B.间接传播
C.间接接触
D.动物携带
参考答案：B
You will be expected to practise at home and know by heart _________ you have learned today next
time you come to class.[ ]
A. that
B. which
C. what
D. where
可引起第二心音A2增强的是（）
A.动脉粥样硬化
B.主动脉瓣狭窄
C.主动脉瓣关闭不全
D.肺动脉高压
E.左心功能不全
