It is reported that between the year 1550 and 1950 about one kind of living things___each year .
Tom’s mother bought quite a lot of things online but spent only $20 _____.
Either you or I _____ going to attend the meeting in the afternoon.
Students should be encouraged to use _____ Internet as _____ resource.
His sister left home in 1998, and_______ ever since.
Sam _____ some knowledge of the computer just by watching others working on it.