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

水泥或石剂量测定应进行两次平行试验，重复性误差不得大于均值的（），否则应重新试验。

A.2%

B.3%

C.1%

D.5%