_____ 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
sweet and fresh, this kind of food is so popular with local people and the tourists．
A．Smell B．Smelling C．To smell D．Smelt
