—How long have you known the doctor ? —         he helped me three years ago.

We’ll go bike riding ________ it doesn’t rain this Sunday. 

—Does your mother often surf the Internet ?—Yes, ___________ she doesn’t buy any thing on line.

–How do you like the two pairs of shoes?--They don’t fit me well. They are ______ too big _____ too small.

Tom didn’t understand the text ________ the teacher explained it to him.