In my view, biology is chemistry, but a little easier than mathematics.
A. a subject so difficult as
B. as difficult a subject as
C. as a difficult subject as
D. difficult as a subject as
网友回答
A. a subject so difficult as
(答案→)B. as difficult a subject as
C. as a difficult subject as
D. difficult as a subject as
解析：固定结构as +形容词+a\an +单数名词 +as 。句意：在我看来生物和化学是一样难的科目但是比数学稍微容易些。