The magician picked several persons from the audience and asked them to help him with the performance.
| A．by accident | B．on occasion | C．at random | D．on an average |
I ______ sooner but I didn’ t know that they were waiting for me.
| A．had come | B．was coming | C．would come | D．would have come |
I oftenthe words I don’ t know in the dictionary or on the Internet.
| A．look up | B．look at | C．look for | D．look into |
_________ is known to us all is that the 2012 Olympic Games will take place in London.
| A．As | B．What | C．That | D．It |
Mr. Stevenson is great to work for—I really couldn’ t ask for a _______ boss.
| A．better | B．good | C．best | D．still better |
He made another wonderful discovery, ______ of great importance to science.
| A．which I think is | B．which I think it is |
| C．which I think | D．I think which is |