Evaluating Statements on Relative Masses

Steps:

• Statement 1 is incorrect: Relative atomic mass is the weighted average of isotope masses, so isotopes directly affect it.
• Statement 2 is correct: Covalent compounds form molecules, which have relative molecular mass as the sum of atomic masses.
• Statement 3 is correct: By definition, relative atomic mass is the ratio to 1/12 the mass of a carbon-12 atom.
• Only statements 2 and 3 are true, matching option C.

Why C is correct:

• Relative atomic mass uses the carbon-12 scale (IUPAC definition), and relative molecular mass applies to covalent molecular compounds.

Why the others are wrong:

• A includes false statement 1 about isotopes.
• B includes false statement 1 and omits true statement 2.
• D includes false statement 1.

Final answer: C