The result was difficult ______.

B 此题目属于be+形容词+不定式结构。 表示“做某事……”。本句的意思是“这个结果难以理解”。类似的还有The question is difficult to answer.

次句型属于省略不定式逻辑主语的句子:
There are so much work (for us) to do.
He's a little boy (for me)to take care.
This is a difficult question (for me) to answer.
The question is difficult (for me) to answer.

B
difficult 后面接to

B be difficult to do sth

B difficult to do sth

B