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
网友回答
A. better as twice
B. twice as the condition
(答案→)C. twice as good
D. twice as better
解析：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。