4.It is said that the early European playing-cards ____ for entertainment and education.
| A．were being designed | B．have designed |
| C．have been designed | D．were designed |
By looking at a problem in as many ways as possible, creative thinkers can find solutions that would _______ remain invisible．
| A．otherwise | B．yet | C．already | D．forever |
—What has made him upset recently?
—_______ alone to face a troublesome milk case．
| A．Left | B．Being left | C．Having left | D．To leave |
—What are you doing, John? Why stop?
—To be on the safe side, we’d fill up the car now for we _______ run out of gas on the way．
| A．must | B．will | C．might | D．should |
When he realized the police had spotted him, the man _______the exit as quickly as possible．
| A．made off | B．made for | C．made out | D．made up |
Bill Gates has created a wonderful “window” ______ people can surf the Internet freely．
| A．that | B．which | C．where | D．when |