In America and Europe, it is __________ to tip anything from 10% to 20%.
| A．customary | B．custom | C．customer | D．customs |
“I’m going to the post office.” “_______ you’re there, can you get me some stamps?”
| A．As | B．While |
| C．Because | D．If |
______ you are at home alone, please don’t leave the door open.
| A．While | B．As |
| C．Before | D．How |
_______ you are alone with her, tell her that you like her.
| A．While | B．As |
| C．After | D．How |
After the war, a new school building was put up ______ there had once been a theatre.
| A．that | B．when |
| C．which | D．where |
The famous scientist grew up _______ he was born and in 1930 he came to Shanghai.
| A．when | B．whenever |
| C．where | D．wherever |