Which is a counterexample to this conjecture?

The sum of any two consecutive integers is a composite number.

A.
16 + 17 = 33

B.
10 + 11 = 21

C.
6 + 7 = 13

D.
7 + 8 = 15

Question

Which is a counterexample to this conjecture? 
 
The sum of any two consecutive integers is a composite number.


 A.
16 + 17 = 33
 
 B.
10 + 11 = 21
 
 C.
6 + 7 = 13
 
 D.
7 + 8 = 15

anonymous · Answer

helps

perl · Answer

A counterexample means any violation of a claim being made. The claim here is that the sum of any two consecutive numbers is composite. A counterexample of this claim are the consecutive numbers 2,3. their sum is 2 + 3 = 5, but 5 is prime.
 can you answer it now?

anonymous · Answer

so what does that mean

perl · Answer

so which of these are two consecutive numbers, but their sum is not composite (their sum is prime)