Which unstable element is used to determine the age of volcanic rock?
argon
carbon-14
potassium
carbon-12

Potassium.

Explanation:

Therefore, the answer is Potassium. You might think, that because we were talking about Argon as well, the answer is both of them, but no. Everything starts with Potassium but it decays into Argon during the process.

smooth muscle is composed of involuntary muscles found within the walls of organs and structures such as the esophagus, stomach, intestines, and blood vessels. those muscles push materials like food or blood through organs. unlike skeletal muscle, smooth muscle can never be under your control.