The computer programs are a puzzle to me. The more I think of them, the more questions I think of .
| A．ask | B．asked | C．being asked | D．to ask |
People ______ long distances frequently have to decide whether they would prefer to go by land, sea or air.
| A．to travel | B．travelled | C．travel | D．travelling |
______ your plans look good, you still need to do some revision work on it.
| A．If | B．Once | C．Although | D．Since |
The prices of houses ______ because the demand of them become more and more great.
| A．are rising | B．rise | C．had risen | D．have been risen |
Compared with the nervousness of driving in the rain or snow, it is ______ to sit in a train without any worry of bad weather.
| A．more tired | B．less tiring | C．less tired | D．even more tiring |
It is dangerous to play with the knife. You ______ hurt yourself.
| A．can | B．may | C．must | D．should |