干粉灭火系统的模拟喷放试验采用干粉灭火剂和自动启动方式，干粉用量不少于设计用量的（）。
A.10%
B.20%
C.30%
D.50%
参考答案：C
This hat is not comfortable and that one is too expensive, so I will _____ of them.[ ]
A. not buy both
B. buy none
C. buy either
D. buy neither
