I paid a fine of 200yuan for speeding. If only I _________ the traffic rules!
| A．had respected | B．respected |
| C．would have respected | D．could respect |
______ I'm willing to help, I do not have much time available．
| A．While | B．When | C．Once | D．Since |
The rise of oil prices made scientists search for new energy resources ______ oil．
| A．replace | B．replacing | C．to replace | D．replaced |
You didn't believe John won the first prize at the speech competition, ______?
| A．did he | B．didn't he | C．did you | D．didn't you |
I had reached a point in my career _____ I needed to decide which way to go．
| A．why | B．which | C．when | D．where |
Here are some new computer programs _____ for home buildings．
| A．designing | B．design | C．to design | D．designed |