上海钢铁工业发达的最主要原因是[ ]
A、劳动力资源丰富
B、临近钢铁消费市场
C、靠近铁矿产地
D、能源充足
答案：B
We went to the beach last Sunday, and we had great fun _______ volleyball. [ ]
A. play
B. playing
C. played
D. to play
活性污泥法的基本设施为（）
A.曝气池
B.沉淀池
C.曝气池、沉淀池
D.曝气池、污泥池
