Question

13. What causes a heartbeat?…………

A. Stretching of the atrium and ventricle muscles
B. Closing and opening of AV and SV Valves
C. Oxygenated blood
per minute
D. The number of times your heart beats

Answer 1

A

Step-by-step explanation:

I think i remember that from heatlth.

Answer 2

A

Step-by-step explanation:

Stretching of the atrium and ventricle muscles