There is clear evidence the most difficult feeling of all to interpret is bodily pain.A.

问题补充：

There is clear evidence the most difficult feeling of all to interpret is bodily pain.

A. what

B. if

C. how

D. that

答案：

A. what

B. if

C. how

(答案→)D. that

解析：

此处的the most difficult feeling of all to interpret is bodily pain 是同位语从句,用来说明evidence是什么,故用that引导同位语从句。意思为有明显证据表明最难以描述的感受来自于身体的伤痛.