So convenient _______ to pay by credit card that more and more people apply for their credit cards.

What were you doing when she dropped in? —I for a while and_________ some reading

______ is a best-known secret in success that get ready in much of our life and you may make the most of the opportunity．

for your timely warning, we _____ into greattrouble— Well, you know we’re friends

Not only _____ a promise， but also he kept it