What subatomic particles make up an atom’s mass number

Basically,  together, the number of protons and the number of neutrons determine an element's mass number: mass number = protons + neutrons. If you want to calculate how many neutrons an atom has, you can simply subtract the number of protons, or atomic number, from the mass number.

Explanation:

d) center of the mid-ocean ridge

give brainleysest

sinserly,

steckh986

not too sure but maybe in the hot springs.