一般普通30w紫外线灯管的使用寿命为（）小时。
A.500小时
B.800小时
C.1000小时
D.1200小时
E.1500小时
参考答案：C
The musicians may start as a group of high-school students, ________ practising their music in someone’s house is the first step to fame.
A．for which
B．for whose
C．for them
D．for whom
决定主板性能的主要部件是（）
A.CPU插槽
B.内存插槽
C.芯片组
D.BIOS
