填空题

Jill bumped into a young zoologist (动物学家) called Adam Briton who absolutely loved crocodiles. One of the things that (11) him about crocodiles was that as part of their (12) behaviors, they fight with other crocodiles and regularly (13) limbs (肢体). What amazed him was that crocodiles (14) in dirty, bacteria-filled water, and yet they never seem to get infections--their limbs heal (15)