作直方图时，当N=50~100时，分成（）组为宜：
A.5
B.6
C.7
D.10
参考答案：A, B, C, D
—Where were you at 7:00 last night?
—I _____ to my mom at home. [ ]
A. write
B. was writing
C. wrote
一般货仓的照明应不少于?
A.50勒克司
B.100勒克司
C.200勒克司
