Câu hỏi:

If you don't have anything _______ to say, I'd rather you kept quiet.

He says he'll tell the authorities but it's just an empty ______.

This is especially worrying when there are about 3,000 plants with values as medicines against cancer, AIDS, heart disease and many other sicknesses.

But we can stop adding the problem while scientists search for answers, and laws are passed in nature’s defense.

Without plants, most water would run off as soon as it falls, taking away valuable soil.

This is especially worrying when there are about 3,000 plants with values as medicines against cancer, AIDS, heart disease and many other sicknesses.

Choose the word whose main stress is placed differently from the others in each group