Question

Cynthia made the conjecture that the sum of any prime number and any composite number is a composite number.

Which equation is a counterexample to her conjecture?

A.
11 + 2 = 13

B.
13 + 2 = 15

C.
11 + 9 = 20

D.
5 + 8 = 13

Answer 1

is 2 composite?

Answer 2

counter example uses the argument but with a case where it is false