衣原体感染的传播方式主要有()
A．呼吸道传播
B．性接触传播
C．垂直传播
D．直接接触传播
E．粪-口途径传播
参考答案：A, B, C, D
We have been excavating layers of ash almost six metres thick, which suggests that they________the fire burning all winter.
A．should keep
B．might have kept
C．should have kept
D．might keep
属于结构抗力的是（）。
A.梁的受弯承载力
B.作用在梁上的均布荷载
C.梁受力后的裂缝宽度
D.梁受力后的的挠度
