Since we know that the deer tick in the larval stage can have different foods, if there are others foods available when the moment it is fed, then it doesn't have to eat the bacterium. To be sure, C says that it only needs to be fed once. If any other food is in front of the lavae, then it won't pick up the baterium, and some human beings won't get infected.
但是为什么deer 不可以eat lcertain other species 很多次呢?正确答案确实是c,可能我没读懂文章