Answer:
B: 51 is not a prime number
Explanation:
To present an indirect proof, we have to assume a statement contrary to the declaration as being correct. In the case of the number 51, to say that prime numbers are not divisible by themselves and 1 is not leading to its proof (C), and to say that 51 is not divisible by itself and 1 is not complete because it is also divisible bt 17. B (51 is not a prime number) will lead to the proof that 51 is a prime number.