近年来,由于开发了多层滤料高速过滤池和()高效过滤器,在滤池进水投加高分子混凝剂作为助滤剂,提高了过滤速度和处理效果。
A.活性炭
B.蛋白质
C.纤维
D.生物膜
参考答案:C
They were ______ to see each other. [ ]
A. pleasure
B. pleasant
C. pleased
D. please