Questions and exercises are given by the computer, which decides ______ to move the students ahead, review an easier level, ____ give more work on the same level.
| A．either, or | B．both, and . | C．whether, or | D．not only, but also |
_________ that he had fallen behind,he tried to work harder.
| A．Having realized | B．Realized |
| C．Realize | D．To realize |
Plastic and rubber won’t _________ electricity,but copper will.
| A．have | B．do |
| C．pass | D．conduct |
________ no need for everybody to discuss the problem again since it has already been solved.
| A．It has | B．There has | C．We have | D．There is |
I didn't like aunt Lucy,who __________ without warning and bringing us presents.
| A．always turned up |
| B．has always turned up |
| C．had always turned up |
| D．was always turning up |
You'd better get all the work _________ before you leave.
| A．finishing | B．to finish |
| C．finished | D．be finished |