What is used to show that an assumption is false? a. inductive reasoning b. counterexample c. pattern d. conjecture

It's b.

Step-by-step explanation:

That would be a counterexample.

For example we might conjecture that all numbers of the form n^2 - n + 41 are prime numbers. This is false because of the counterexample if n = 41 then 41^2 - 41 + 41 is divisible by 41.

I think conjecture is the answer