By the time I reach the age of sixty, I hope to be healthy enough to travel ___________ .

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

Since Tom_____ downloaded a virus into his computer, he can not open the file now.

The traffic problems have severely affected economic development. ________, we must spare no efforts to solve them.

The workers have produced _______ this year as they did two years ago.