Additives _____ protective layers on metal surfaces guarding them against corrosion.A.dama

The chemical factory was demolished _________ protecting the environment.A. in spit

______ is a low，even layer of dark grey clouds，with light and dark patches.A.CirrostratusB

The ozone layer plays as great a role in the stability of spaceship Earth as ______ the wa

The new visa policy aims at______.A. protecting S

Land protected by the National Trust_________.A.c

57._________A.keep B.stop C.protect D.prevent