On the surface of the water________, which spoiled the beautiful scenery of the park.

A．some dead leaves did float

B．did float some dead leaves

C．floated some dead leaves

D．did some dead leaves float

下面哪项不是酸雨的有害作用

A．使皮肤癌的发生率增加

B．破坏农田和植被的化学组成

C．增加土壤中重金属的水溶性

D．影响土壤中生物的生存

E．增加输水管材中金属化合物的溶出