Radium salts, which have been found to _____ in bones, give rise to cancers of the bone.
| A．pile up | B．build up | C．keep up | D．pull up |
----- In recent years,___ problem of global warning has been very serious.
------That’s right. People are facing ____ number of natural disasters now.
| A．不填; | B．a; the | C．the; a | D．a; a |
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 |
_____ inviting guests and not treating them properly!
| A．Strangely | B．Fantastically | C．Surprisingly | D．Fancy |
_____ 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 |