管道运输就其铺设工程可分为（）。
A.水中管道
B.地下管道
C.地面管道
D.系泊管道
E.架空管道
参考答案：B, C, E
A neighbour helped to keep our dog. It ______ while we were on holiday. [ ]
A. was taken care
B. took care of
C. is taken care of
D. was taken care of
层片是指在群落中属同一______的生物不同种个体的总和。
