A. training
B. said
C. waiting
D. main

A．the production of new industrial goods
B．increased amounts of unnatural substance
C．our ever-increasing population
D．the release of artificial substances into the environment

A．He was afraid that someone would steal his box.
B．Because he wanted to climb up along the rope.
C．He fastened the end of the rope in order to keep the box unmoved.
D．Because he wanted to prevent the box from coming down.