－Sorry，Betty！I forgot to inform you of the change of time.
－________．
| A．Forget it | B．Don't mention it |
| C．That's right | D．With pleasure |
It is hoped that these new discoveries will throw ____ light upon such ____ mysterious natural phenomena.
| A．a; a | B．a; / | C．/; a | D．/; / |
My bicycle is nowhere to be found. Who ___ have been using it?
| A．should | B．must | C．could | D．might |
He cut off the electricity immediately he found the dangerous situation, thus ____ a fire accident.
| A．prevented | B．to prevent | C．would prevent | D．preventing |
But at other moments you will find him gentle and weak, _____ he cries about the lost lives of people drowned in ships that have sunk.
| A．as with | B．as for | C．as to | D．as when |
They form a polar molecule, ____ is, ____ with a slightly positive end and a slightly negative end.
| A．which; that | B．it; one | C．that; one | D．one; that |