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

I can’t finish this job by Friday. You expect too much of me.

The committee is discussing the problem right now. It will_____ have been solved by the end of next week.

.-----How do you find the dictionary? -------It’s useful,_________for beginners of English.

Joe worked so hard that ________ he made himself ill.