问题
选择题
My car’s performance is ___ since the engine’s been tuned and the tires have been changed．
A．better as twice
B．twice as the condition
C．twice as good
D．twice as better
答案
答案：C
考查倍数问题。倍数 + as + 形容词，句意：这辆汽车调了发动机和换了轮胎以后性能好了一倍。选C。