The largest three digit prime number is

Option(A):  999 is divisible by 3. So it is not a prime number.

Option(B):  993 is divisible by 3. So it is not a prime number.

Option(C):  997 is divisible by 1 and itself only. So it is the largest three digit prime number.

Option(D):  987 is divisible by 3. So it is not a prime number

i.e. A,B, and D has more than two factors. But C has only 2 factors and it is largest three digit prime number