He fell asleep immediately last night; he must ________ (be) very tired.

I shall never forget ________ (meet) the late Premier Zhou during his inspection of our factory.

Herefusedtotelluswhetherhe________(undertake)thejob.

Onlywhenyouhaveobtainedsufficientdata________cometoasoundconclusion.

A beam of light will not bend round corners unless ________ (make) to do so with the help of a reflecting device