用如图所示的滑轮组成最省力的滑轮组提升木桶的绕绳方法。
I'm still hungry. Could I have two _________ pieces of bread , please? [ ]
A. much
B. many
C. more
D. most
油罐投用前需检查进出口阀门、人孔、清扫孔等处的（）是否牢靠。
A、静电
B、盲板
C、紧固件
D、密封件
