Lab workers must wear protective ______.

Global warming caused by human being’s casual behaviour has become a major _______ for people all over the world.

Thanks to the modern electrical_____, housework nowadays has been made easier and easier.

But the unpleasant feeling of coldness disappeared at the _______ of his students pouring out of their classroom to give him a warm, wordless welcome.

The public ______ of the environmental problem will make the government take it seriously.