The isotope of hydrogen that has two neutrons is called a. hydrogen. b. deuterium. c. tritium. d. dihydrogen.

C.Tritium

Explanation:

Isotopes are forms of an element with different mass number but same atomic number. Mass number is the sum of the number of protons and neutrons in the nucleus of an atom, while atomic number is the number of protons.

Mass number = protons +neutrons.

Atomic number = protons only

We can say that mass number = atomic number + number of neutrons.

The number of neutrons is what differentiates the isotopes of an element.

For hydrogen element, it has three isotopes namely; protium, deuterium and tritium which have 0,1 and 2 neutrons respectively. Thus the answer is C

yes the answer is total mass in unchanged   : )