一道题里的 rival 的用法

Bryon possessed powers of observation that would have made him a great anthropologist and that makes his letters as a group the rival of the best novels of the time.

a.makes his letters as a group the rivals of

b.makes his letters as a group one to rival

c.makes his letters a group  rivaling

d.make his letters as a group the rival of

e make his letters a group which is the rival of

答案是 d 

请教一下rival 在D 中的用法

og 中没有提到这种用法 啊