Answer the following question given this paragraph: 

Cardiac muscle is found only in the walls of the heart. It is striated, or striped, because its muscle fibers are arranged in bundles. Contractions of cardiac muscle are involuntary. This means that they are not under conscious control. When cardiac muscle contracts, the heart beats and pumps blood.


Q: When cardiac muscle contracts, the heart does what?

 Choices:

- cardiac arrest

- irregular heartbeat

- heart murmur

- pumps blood

A:
pumps blood
