Every possible means ______ to prevent the air pollution, but the sky is still not clear.
| A．has been used | B．have been used | C．is used | D．are used |
Nowadays everything strange is____strange. That is to say, any unexpected ____thing is possible to happen.
| A．something | B．anything | C．nothing | D．everything |
Hello.You_____ 68442936. I’m sorry I’m unable to answer your call right now.
| A．reached | B．have reached | C．are reaching | D．had reached |
________ him before, I didn't recognize him.
| A．Having never seen | B．Never seeing | C．Not seeing | D．Having not seen |
As a teacher, I seldom give my students so difficult a problem ________ they can not work out.
| A．that | B．if | C．in order that | D．as |
None of us had expected the middle-aged engineer died ____ his design uncompleted.
| A．from | B．without | C．of | D．with |