灭火器压力表指针处于（）时表示可以正常使用。
A、绿色区域
B、红色区域
C、黄色区域
D、蓝色区域
参考答案：A
Only when________the data again________that there was a mistake. [ ]
A. they had studied；did they realize
B. they had studied；realized they
C. had they studied；did they realize
D. had they studied；realized they
麻花钻横刃斜角的大小是由后角大小决定的。后角大时，横刃斜角就减小。( )
