正常情况下，一个细胞连续分裂三次后可以形成（）
A.无数个细胞
B.8个细胞
C.6个细胞
D.3个细胞
参考答案：B
The teacher asked Alice _____ yesterday. [ ]
A. why she misses school
B. why does she miss school
C. why she missed school
D. why did she miss school
地下洞室如必须穿越含瓦斯的煤系地层，则应尽可能与煤层走向（）
A.平行
B.垂直
C.45°斜交
D.以上均可
