Wolves generally avoid human settlements. For this reason, domestic sheep, though essentially easy prey for wolves, are not usually attacked by them. In Hylantia prior to 1910, farmers nevertheless lost considerable numbers of sheep to wolves each year. Attributing this to the large number for wolves, in 1910 the government began offering rewards to hunters for killing wolves. From 1910 to 1915, large numbers of wolves were killed. Yet wolf attacks on sheep increased significantly.

Which of the following, if true, most helps to explain the increase in wolf attacks on sheep?

1. Populations of deer and other wild animals that wolves typically prey on increased significantly in numbers from 1910 to 1915.
2. Prior to 1910, there were no legal restrictions in Hylantia on the hunting of wolves.
3. After 1910 hunters shot and wounded a substantial number of wolves, thereby greatly diminishing these wolves’ ability to prey on wild animals.
4. Domestic sheep are significantly less able than most wild animals to defend themselves against wolf attacks.
5. The systematic hunting of wolves encouraged by the program drove many wolves in Hylantia to migrate to remote mountain areas uninhabited by humans.

敢问为何选c呢？文中不是说wolf attacks on sheep 上升了吗？