Answer the following question given this paragraph: 

Hair, hair follicle, and oil glands. The oil, called sebum, helps to prevent water loss from the skin. The sebaceous gland secretes sebum, which waterproofs the skin and hair.


Q: What does the sebaceous gland secrete which waterproofs the skin and hair?

 Choices:

- pus

- progesterone

- collagen

- sebum

A:
sebum
