The smallest value of n, for which 2n + 1 is not a prime number is  Choices:
A) 3	B) 4	C) 5	D) 6	E) 7

Rationale: "sol . = ( 2 × 1 + 1 ) = 3 , = ( 2 × 3 + 1 ) = 7 , = ( 2 × 4 + 1 ) = 9 , which is not prime . therefore n = 4 . answer b"
Answer: B