Correct Answer - Option 4 :
50 : 76
All numbers are divisible by 12 except 50:76.
1) 84 : 96 → Both numbers are divisible by 12.
2) 24 : 48 → Both numbers are divisible by 12.
3) 12 : 72 → Both numbers are divisible by 12.
4) 50 : 76 → Both numbers are divisible by 2.
Hence, 50 : 76 is the correct answer.