challenges

[belly_ttt]

The new discovery, along with previous reports of other 11000-year-old human sites in South America, __ the theory that the first New World settlers immediately trekked inland after crossing the Bering Strait from Asia, mainly hunted big game, and moved into South America along the Andes Mountains.a) challengesb_ challengingThe answer turns out to be b but I think a is OK. why not a but b?

[Anglika]

I don't know. #a is correct.

The logic of the sentence is not carried through with "challenging".