It is not until recently ______ the scientists have found proof of there being water on Mars.
| A．when | B．that | C．how | D．what |
Leaves are found on all kinds of trees, but they differ greatly __________ size and shape.
| A．on | B．from | C．by | D．in |
__________ what the six blind men said sounded! I can't help laughing!
| A．How foolishly | B．How foolish |
| C．What foolishly | D．What foolish |
—Doctor, it seems you like to work with animals.
—Yes, I think animals should __________ as our friends.
| A．regard | B．regarded | C．to regard | D．be regarded |
Her parents require that she __________ TV after she finishes her homework.
| A．watched | B．watches | C．watch | D．will watch |
In America and Europe, it is __________ to tip anything from 10% to 20%.
| A．customary | B．custom | C．customer | D．customs |