[讨论]大全补充 -218 骆驼驯化

poplars

218.
                The domesticated camel, which some scholars date around the twelfth century B.C., was the key to the development of the spice trade in the ancient world.

(A) The domesticated camel, which some scholars date

(B) The domesticated camel, which some scholars having thought to occur

(C) Domesticating the camel, dated by some scholars at

(D) The domestication of the camel, thought by some scholars to have occurred（D）

(E) The camel’s domestication, dated by some scholars to have been

我想问的是为什么主语是domestication的情况下，D后面还可以用have而不是has啊？