He walked with his eyes ____ his book.(A) fixing (B) fixed并说明原因,横线后面漏了on

B

选B
因为眼睛是人控制的，所以sb fix one's eyes on sth

B.
with+n.+非谓语动词（如不定式,完成时等）是独立主格结构,作状语,非谓语动词主动还是被动由with后面的名词与它的关系决定,
因为eyes是被人fix on his book,所以eyes be fixed on his book.

少打了个介词on吧，fix可是不及物动词。
be fixed on ,固定搭配，这里把be动词省略了，因为fix和eye是动宾关系，用被动表达。
选B。