The correct option is D 4, 5
Co prime numbers have no common factors other that 1.
Option a: 2 and 110 has 2 as a common factor.
Option b: 10 and 20 has 2, 5 and 10 as common factors.
Option c: 9 and 24 has 3 as a common factors.
Option d: 4 and 5 has no common factor other than 1. Hence they are co prime numbers.
So, correct option is 'd'.