组件组装误用同孔数、大孔径喷丝板，上机后可能出现的问题是（）。
A.组件压力低
B.喷丝头拉伸比减小
C.纤度异常
D.含油率低
参考答案：A
在下列生物中，不属于真菌的是： （ ）
A．酵母菌
B．细菌
C．青霉
D．蘑菇
In the last few years, they ______ three major concerts. [ ]
A. have had
B. had had
C. had
