血吸虫病的传播途径为（）。
A.呼吸道
B.消化道为主
C.呼吸道和消化道
D.皮肤粘膜接触
E.蚊子媒介
参考答案：D
A．Because she could not sleep well at night.
B．Because she hoped to earn more money.
C．Because she could not find a daytime job.
D．Because she needed a change and a lighter job.
20CrMnTi的含碳量是0.2%。（）
