All flights ________ owing to the heavy fog, many passengers could do nothing but take trains.
| A．to be cancelled | B．were cancelled |
| C．have been cancelled | D．having been cancelled |
_______ basic first-aid techniques will help you respond quickly to emergencies.
| A．Known | B．Having known |
| C．Knowing | D．Being known |
People develop _______ preference for a particular style of learning at _______ early age and these preferences affect learning.
| A．a; an | B．a; 不填 |
| C．不填; the | D．the; an |
She ________ someone, so I nodded to her and went away.
| A．phoned | B．had phoned |
| C．was phoning | D．has phoned |
I think _______ is no need for us to comment on his action: it speaks for itself.
| A．it | B．that | C．there | D．this |
----- It’s too strange that these people should laugh when their relatives die.
----- That is the local custom ______ the seventeenth century.
| A．dates back to | B．dated back to |
| C．dating back to | D．had dated back to |