________ an hour every day has made a considerable difference to my health.
| A．Having walked | B．Walk |
| C．Walking | D．Walked |
If the boy had _____ the dog alone it wouldn't have bitten him.
| A．set | B．left | C．had | D．put |
The generation _____ makes it difficult for parents to understand their children's opinions.
| A．division | B．gap | C．separation | D．interval |
With sufficient scientific information a manned trip to Mars should be _____.
| A．obtainable | B．potential | C．considerable | D．feasible |
_____ it is a good thing I did not get the post I had applied for, though I must admit that I was disappointed at the time.
| A．By the way | B．In a way | C．In the way | D．In no way |
The two things are the same in outward form but different _____.
| A．in addition | B．in brief | C．in common | D．in essence |