為什麼是放形容詞而不是副詞呢?

Research at Firmatek are working on a new material that will be twice as___as ordinary concrete.
(A)durably
(B)durable
(C)durability
(D)durableness
答案是 B
解答是說: 根據前面的will be可得知此處應填選形容詞,所以選擇B
請問這是為什麼?
5 個解答 5