what is the value of m?

[VJesus12]

m=?

1) 5 is a factor of m
2) m is a prime number

The OA is C.

Why is C the correct answer? I got confused.

[Brent@GMATPrepNow]

m=?

1) 5 is a factor of m
2) m is a prime number

Target question: What is the value of m?

Statement 1: 5 is a factor of m
There are several values of m that satisfy statement 1. Here are two:
Case a: m = 5
Case b: m = 10
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: m is a prime number
There are several values of m that satisfy statement 2: m = 2, m = 3, m = 5, m = 7, m = 11, etc
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
Statement 2 tells us that m is a prime number. This means that m has EXACTLY 2 factors: 1 and m
Statement 1 tells us that 5 is a factor of m
This means that m MUST equal 5
Since we can answer the target question with certainty, the combined statements are SUFFICIENT

Answer: C

Cheers,
Brent