Answer: The given statement is true.
Step-by-step explanation:
Average atomic mass is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.
The equation used to calculate average atomic mass follows:

Chlorine element has 2 naturally occurring isotopes: Cl-35 and Cl-37
Percentage abundance of Cl-35 isotope = 75 %
Percentage abundance of Cl-37 isotope = 25 %
Average atomic mass of chlorine element = 35.45 amu
As, the average atomic mass of chlorine is closer to the mass of Cl-35 isotope. This means that the average atomic mass of an element lies closer to the isotope having high percentage abundance or teh most commonly occurring isotope.
Hence, the given statement is true.