Explanation:

- Let's analyze the relationship in each of the given pairs:

- Option 1: 43:3

- The prime factors of 43 are just 43 (since 43 is prime).

- Gives a direct relation between the first number and a prime.

- Option 2: 71:5

- The number 71 is a prime number.

- A non-matching relation, as 71 is expressed with an unrelated smaller number.

- Option 3: 126:9

- 126 = 2 × 3² × 7

- There's a presence of the number 9 whose factors are square of 3.

- Option 4: 155:11

- The prime factors of 155 are 5 and 31.

- 11 doesn't relate mathematically here.

- The odd one out based on inconsistent pairing is Option 3: 126:9.

- Option 3 is the correct answer.

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