Tom is so independent that he never asks his parents’ opinion ________ he wants their support.
A.since B.once
C.unless D.after
（2016·天津）_____the average age of the population increases, there are more and more old people to care for.
A.Unless B.Until
C.As D.While
________ some people are motivated by a need for success, others are motivated by a fear of failure.
A.Because B.If
C.Unless D.While
The companies are working together to create ________ they hope will be the best means of transport in the 21stcentury.
A.which B.that C.what D.who
You won’t find paper cutting difficult _____you keep practicing it.
A.even if B.as long as C.as if D.ever since
If you want to lead a happy life, you’d better learn to accept life ______ it is.
A.as B.that
C.which D.where
