数字相机的感光度一般都设置为高感光度。因为此时的图像质量较好。( )
参考答案：错
If there were no examinations, we should have _______ at school. [ ]
A. the happiest time
B.a more happiest time
C. much happiest time
D.a much happier time
构成细菌毒力的是（）。
A.基本结构
B.特殊结构
C.侵袭力和毒素
D.分解代谢产物
E.侵入机体的途径
