Answer the following question given this paragraph: 

Cysts may develop in the ovaries. A cyst is a sac filled with fluid or other material. Ovarian cysts are usually harmless and often disappear on their own. However, some cysts may be painful and require surgery.


Q: What is a sac filled with fluid or other material?

 Choices:

- a lesion

- Golgi apparatus

- a receptacle

- a cyst

A:
a cyst
