The price of the flat now is ____ that last year. A. as twice high as B. twice more expensive

The price of the flat now is ____ that last year. A. as twice high as B. twice more expensive
The price of the flat now is ____ that last year.
A. as twice high as\x05\x05\x05B. twice more expensive than\x05
C. as high as twice\x05\x05\x05D. twice the amount of
选哪个？为什么？