假设预热器C5落料温度为970℃，它属于（）信号.
A.AI
B.AO
C.DI
D.DO
参考答案：A
Can you imagine a person _____ in the cultural revolution for doing nothing wrong? [ ]
A. putting into prison
B. to stay in the prison
C. being put into prison
D. to put into prison
在显微镜视野下，判断毛细血管的依据是（ ）
A．没有红细胞通过的血管
B．红细胞呈单行通过的血管
C．流鲜红色血液的血管
D．流暗红色血液的血管
