He kept looking at her, wondering whether he _____ her somewhere.
| A．saw | B．has seen | C．sees | D．had seen |
Not until Mary reads her composition the second time ___________the spelling mistake.
| A．did she notice | B．she noticed | C．does she notice | D．she has noticed |
-Look! Someone __________sofa.
-Well,it wasn`t me.I didn`t do it
| A．is cleaning | B．was cleaning | C．has cleaned | D．had cleaned |
.I was about to get on the bus __________my wife phoned me to back home at once.
| A．when | B．while | C．until | D．after |
We must do what we can to ____________the river ______________.
| A．protect; against polluting | B．stop; polluting |
| C．keep; being polluted | D．prevent; from being polluted |
Paper produced every year is _______________the world`s production of vehicles.
| A．three times the weight | B．the three times weight |
| C．as three times heavy as | D．three times as heavier as |