A classmate states, “Because 6 is divisible by 2, every number divisible by 2 is also divisible by 6.” Which principle justifies that finding the number 8 is enough to reject this statement?
a) \text{A single example can prove a universal statement true}
b) \text{One counterexample suffices to disprove a universal statement}
c) \text{Two counterexamples are required to disprove a universal statement}
d) \text{A single exception only weakens the claim; it cannot fully reject it}