h teachers are supposed ______theirstudents a test in class, even after class, ______better teaching results.

___ is left over may be put into the refrigerator, ____ it will keep for two or three weeks.

He focused his effort ____the house___sale for fear that the prices of them would go up suddenly.

’t seen you for ages! Where have you been—I went to Ning Xia and _______ there for a year, teaching as a volunteer.

We can broaden our horizons through _________ to new things.