With all the books he was interested in he left the library and went back to his dorm.A

问题补充：

With all the books he was interested in ， he left the library and went back to his dorm.

A. borrowed

B. borrowing

C. to borrow

D. borrow

答案：

(答案→)A. borrowed

B. borrowing

C. to borrow

D. borrow

解析：A考察非谓语动词。分析句中结构可知，he was interested in是定语从句，修饰books ,句子的前面半部分是with+宾语+宾语补足语的复合结构，由于Bookstore是被借出的，因此要使用borrowed。故A正确。