蓄电池组是向（）供电的直流电源。
A.控制负荷；
B.交流不停电电源系统；
C.直流油泵；
D.事故照明负荷。
参考答案：A, B, C, D
---Do you know Miss Tang?
---Yeah, she is an excellent teacher, ______she is famous ______a wonderful singer in our school.
A．or; for
B．but; as
C．and; for
D．so; as
以下电子排布式是激发态原子的电子排布的是
A．1s22s1
B．1s22s22p1
C．1s22s22p63s2
D．1s22s22p63p1
63s2