I’ll come to pay a visit to you if _______ this weekend.
| A．you’re convenient | B．it is convenient for you |
| C．you feel convenient | D．it is convenient with you |
In much of the animal world, night is the timefor sleep-pure and simple.
| A． | set aside | B． | set down | C． | set off | D． | set up |
Butterflies ______ a sweet liquid produced by flowers, which bees and other insects collect.
| A．carry on | B．feed on | C．put on | D．focus on |
According to the law, all foreigners have to ______ with the local police within two weeks of arrival.
| A．associate | B．dispute | C．negotiate | D．register |
While intelligent people can often ______ the complex, a fool is more likely to complicate the simple.
| A．sacrifice | B．substitute | C．simplify | D．survive |
Carbon dioxide, which makes a ______ between us and the sun, prevents heat from getting out of the atmosphere easily, so the earth is becoming warmer.
| A．difference | B．comparison | C．connection | D．barrier |