We're looking for a flaw in the argument. The argument tells us that domesticating animals is cooperative, and therefore needs a sophisticated means of communication, which language provides. The argument then concludes that language developed PRIMARILY to facilitate animal domestication. But this seems too specific right off the bat. Isn't it more likely that language developed for another reason/myriad of reasons, and then happened to be useful for domesticating animals? The argument jumps from "A is necessary for B" to "A developed in order for B to be possible." We can see why this is fallacious with another example: perhaps ketchup is necessary for a child to eat his scrambled eggs. But was ketchup invented for the purpose of making sure the child could eat those eggs? Of course not. (E) perfectly encapsulates this flaw. Hope this helps!