Why is only carbon used and not any other element for defining atomic mass unit?

Why is only carbon is used and not only other element for defining atomic mass unit?

Give the values of Electron, proton and neutron in terms of united atomic mass unit(U).

What are the units of Atomic mass ?

Which symbol replaces the unit of atomic mass, amu?

Which of the following represents a unified atomic mass unit (lu)?

Calculate the spin only magnetic moment of divalent cation of element having atomic number 27.

Give scientific reasons : Atomic number is a more fundamental property of an element than its atomic mass.

Define the term: Atomic mass number

The fractional atomic mass of an element is due to