It was decided to _____ the search when there was no hope of finding the missing girl alive.
| A．call off | B．take up | C．keep off | D．ring up |
No one knows ______effects the GM material might have on the food chain.
| A．what | B．which | C．whose | D．how |
With drink and food ____, the prisoner had to walk out of the cave where he was hiding.
| A．running out | B．run out | C．use up | D．using up |
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 |