He have come here yesterday, he?
| A．mustn’t;did | B．couldn’t;has | C．mustn’t;haven’t | D．must;didn’t |
Not ______that is best for nature is good for people.
A anything B nothing C something D everything
The bell __ the end of the period rang, __our heated discussion.
| A．indicating, interrupting | B．indicated, interrupting |
| C．indicating, interrupted | D．indicated, interrupted |
_______cloning human embryos is not legal in many countries, some scientists are already pushing ahead with research in order to produce a cloned human baby.
| A．While | B．When | C．Since | D．if only |
________ the programme, they have to stay there for another two weeks.
A Not completing B Not completed
C Not having completed D Having not completed
When the boss came in, these workers pretended to________ carefully.
| A．working | B．be working |
| C．work | D．have been working |