Which of the following is a pair of co-primes

A (16, 62)

B (18, 25)

C (21, 35)

D (23, 92)

Correct Answer: Option B

solution: H.C.F of 16, 62 is 2; H.C.F. of 18, 25 is 1;

H.C.F. of 21, 35 is 7; So option b is right ans.