Product of two natural numbers is 7. Then, the sum of reciprocals of their squares is	Choose the correct choice from the following answers
A) 50 / 49  B) 1 / 289  C) 290 / 90  D) 290 / 19  E) none of these

Rationale: "explanation : if the numbers are a , b , then ab = 7 , as 17 is a prime number , so a = 1 , b = 7 . 1 / a 2 + 1 / b 2 = 1 / 1 ( 2 ) + 1 / 7 ( 2 ) = 50 / 49 option a"
Answer: A