The number of common prime factors of 60, 75 and 105 is

1. 2

2. 3

3. 4

4. 5

Prime factorisation of the given numbers are:

60 = 2 × 2 × 3 × 5

75 = 3 × 5 × 5

105 = 3 × 5 × 7

The common prime factors of 60, 75 and 105 are 3 and 5 — that is 2 common prime factors.

Hence, option 1 is the correct option.