It's dangerous to let the children who are _____ go swimming in the river.
| A．too young to | B．so young | C．not old enough to | D．so old |
It’s already 10’clock. I wonder how it ____ that she was two hours late on such a short trip.
| A．came over | B．came out | C．came about | D．came up |
Many strange new means of transport have been developed in our century, the strangest of _____ being perhaps the hovercraft(气垫船).
| A．which | B．them | C．that | D．it |
___ the temperature might drop, coal was prepared for warming.
| A．To consider | B．Considered | C．Considering | D．To be considered |
We had a really bad time about six months ago but now things are ____.
| A．looking up | B．coming up | C．making up | D．turning up |
--- The research on the new bird flu virus vaccine is challenging and demanding. Who do you think can do the job?
---____ my students have a try?
| A．Shall | B．Must | C．Will | D．May |