One of the effective ways to lessen environmental pollution is the reservation and protection of more swamps.

A．vast thick corals

B．pockets of wetland

C．warm volcanoes

D．millions of bees and wasps

骨与关节结核最常见的好发部位是（）

A.膝关节

B.脊柱

C.肘关节

D.踝关节

E.髋关节