阅读下面材料，并完成材料后的问题。 材料1 Tom: Hello Alice. I'm interested in your work saving birds! What do you think is the most difficult part of your work? Alice: Well ... I suppose it's saving wild birds covered in oil. That's the most difficult of all. Tom: How does that happen? Alice: The oil comes from boats. It floats on the water and covers the bird's feathers when they swim through it. Tom: That sounds terrible. What do you do about it? Alice: The first thing we do is to make sure the bird hasn't tried to clean itself with its beak. As it does so, the bird eats some oil and becomes sick. Tom: Oh dear! Do the birds always die? Alice: Sometimes ... but we try to save them. Birds use their feathers like a raincoat to keep out cold water. When feathers are covered in oil, they stick together and a bird's skin gets cold in the water. So without help the bird would die of cold! 材料2 Scientists have discovered that when chimpanzees have stomach pains, typically because of intestinal parasites, they look for a certain plant to eat, Lippea. It is common in the jungles where chimpanzees live, and it contains chemical substances effective against many parasites. Lippea is not the only natural medicine in the chimpanzees' cabinet. They may actually use up to thirty different plants—for different problems. Interestingly, the local people make use of many of the same plants for medical purposes. It is almost certain that chimpanzees discovered these herbal remedies before humans.