In which set of numbers every pair is coprime to each other?

Answer: Option D

Given,
35, 48, 55
24, 35, 49
42, 55, 69
21, 32, 43
Concept used:
Co-prime numbers = Co-prime numbers are ones with just one common element, which is 1.
Calculations:
According to the question,
Factors of (35, 48, 55) = 5, 1
⇒ 35 = 5 × 7 × 1
⇒ 48 = 2 × 2 × 2 × 2 × 3 × 1
⇒ 55 = 5 × 11 × 1
Factors of (24, 35, 49) = 7, 1
⇒ 24 = 2 × 2 × 2 × 3 × 1
⇒ 35 = 5 × 7 × 1
⇒ 43 = 7 × 7 × 1
Factors of (42, 55, 69) = 3, 1
⇒ 42 = 2 × 3 × 7 × 1
⇒ 55 = 5 × 11 × 1
⇒ 69 = 3 × 23 × 1
Factors of (21, 32, 43) = 1
⇒ 21 = 3 × 7 × 1
⇒ 32 = 2 × 2 × 2 × 2 × 2 × 1
⇒ 43 = 43 × 1
∴ The set of number which are co-prime number are (21, 32, 43)