23．- Why weren’t you at the meeting?
- I ________ for a long distance call from my sister in America.
| A．was waited | B．was waiting | C．has waited | D．have been waiting |
I looked up and noticed a snake ______ its way up the tree to catch its breakfast.
| A．to wind | B．wind | C．winding | D．wound |
Tom took a taxi to the airport, only _____ his plane high up in the sky.
| A．finding | B．to find | C．being found | D．to have found |
（2012辽宁卷）The old couple often take a walk after supper in the park with their pet dog them.
| A．to follow | B． following | C． followed | D． follows |
（2012辽宁卷）This machine is very easy . Anybody can learn to use it in a few minutes.
| A． operating | B． to be operating | C． operated | D． to operate |
_____to work overtime that evening, I missed a wonderful film.
| A．Having been asked | B．To ask | C．Having asked | D．To be asked |