To determine which option makes Mary's statement false, we need to analyze each option one by one:
Option A) 6 - This number is divisible by both 2 and 3, so Mary's statement is true for this option.
Option B) 8 - This number is divisible by 2, so Mary's statement is true for this option.
Option C) 11 - This number is not divisible by either 2 or 3, so Mary's statement is false for this option.
Option D) 15 - This number is divisible by 3, so Mary's statement is true for this option.
Therefore, the correct answer is option C) 11. This option makes Mary's statement false because 11 is not divisible by either 2 or 3.