The chemistry teacher asked the students ________ more attention _________the lab clean.
Hainan celebrated(庆祝)her twentieth birthday ____ April 26, 2008. A. in B. at C. on
–What do you call this in English? –It’s stamp. It is used ____ sending letters.
Nobody can stop me ____ working hard at English.
Our sports meeting has been ____ till next Monday because of the bad weather.
Do you know the young lady ____ your mother is talking?