.—Do you like the material? —Yes, it ______ very soft. (MET1994 ) 

—Is there any possible way to help them get rid of such a bad habit?—To tell the truth, it’s very hard. But we ________ on this problem, trying to improve the situation .

It _____ about twenty years since CCTV ____ to broadcast English programs.

The changes of the plants and animals in an area ________ from differences in climate and the           nature of the country.

The last decade of the 21st century ________ the rapid, steady development of China in various fields.