He has been working too hard., he needs to have a rest.

Nature reserves are very important for preserving many animals and plants, which would _______ run the risk of becoming extinct

e out for some time. ______ anything important happens, call me up immediately.

____ from space, the earth, with water ____ seventy percent of its percentage, looks a “blue ball”. [ ]

I had been puzzled over the problem for over an hour without any result, all at once a solution flashed across my mind