Here are the answers for the numbered blanks:

- **Question 37:** C. Some animals can be trained to help people
- **Question 38:** A. but they need care and attention
- **Question 39:** D. Many wild animals face threats from human activities
- **Question 40:** B. help keep the balance of nature

So the answers are:
- Question 37: C
- Question 38: A
- Question 39: D
- Question 40: B