Staements I: The nucleus `._Z^AX` is having atomic mass as well as its mass number as `A`.
Staements II: Mass number of an element is an integer that specifies an isotopes and has no units, while atomic mass is generally not an integer.

Answer

d

Explanation

Atomic mass and mass number are different. Mass number is simply representing number of nucleons, while atomic mass is the average of the masses of isotopes of a given element and has units of u (atomic mass unit).