On April 20,2013, a serious earthquake happened in Ya’an. Many people in it.
I was about to enter the office ______ I heard someone cry “ Earthquake!” loudly outside.
I am considering buying ______ used car for its lower price.
It is clever ________ you ________ me work out the maths problem.
There is ________ in the classroom, so we can see ________.
We should prevent the children ________ the bad programmes.