.－Who taught _____ to swim?－I learned it by _____.

What do you think of the four classics (名著)of China?－I hear that they are wonderful, but I’ve read _______ of them.

Although Fleming discovered Penicillin, it was over a decade ______ someone else turned it into the great drug of the

What a nice model ship!– Thank you. It me three days to make it.

She spent four weeks which she could afford _______ around the country, promoting her new album.