Mary is very clever and_____ worth teaching , but her brother is not .Look he is now _____ asleep in class.

It is commonly assumed that the growth of GDP and the development of people’s living conditions are not _______cause and effect.

My parents will move back into town in a year or _______ .

 Smallpox, a kind of disease, has now died ________.

．We’ve published large quantities of books. This year______ we’ve published three million copies.