Weighted Average of Isotope Masses Steps:

• Convert percentages to decimal fractions: 47.81% = 0.4781, 52.19% = 0.5219.
• Multiply each mass by its fraction: 150.92 × 0.4781 ≈ 72.15, 152.92 × 0.5219 ≈ 79.81.
• Sum the products: 72.15 + 79.81 = 151.96. Why B is correct:
• Relative atomic mass is the abundance-weighted average of isotope masses, yielding exactly 151.96. Why the others are wrong:
• A: Underestimates by ignoring higher abundance of heavier isotope.
• C: Minor rounding error upward from precise calculation.
• D: Overestimates due to slight misweighting of abundances.

Final answer: B