问题补充：
.I want to buy a rope which is this one.
A. twice as longer as
B. as twice long as
C. twice the length of
D. as twice as
答案：
A. twice as longer as
B. as twice long as
(答案→)C. twice the length of
D. as twice as
解析：考查倍数。倍数的表达有：倍数 + as + 形容词或副词的原级 + as + 其他；倍数 + 形容词（或副词）的比较级 + than + 其他；倍数 + the size / height / length / width. etc. + of + 其他。故选C。
