vishallchoudhary, Docmba68 is right, but let me add the numbers to make it click.
The trap in Statement 1 is a classic one. You're confusing the ratio of CABINS with the ratio of PEOPLE. Those are two very different things.
Statement 1 tells you: boys occupy 1.2x as many cabins as girls. Say girls occupy 5 cabins and boys occupy 6 cabins. That's all we know about cabin counts. The question asks for the ratio of boys to girls as actual PEOPLE.
Here's the problem: if each boys' cabin has 3 people and each girls' cabin has 3 people, then boys = 18, girls = 15, ratio = 18:15 = 6:5. But if each boys' cabin has 2 people and each girls' cabin has 4 people, then boys = 12, girls = 20, ratio = 12:20 = 3:5. Two completely different answers from the same cabin ratio.
Statement 1 alone: insufficient.
Statement 2 says: either 12 boys or 12 girls occupy each cabin. So every cabin has exactly 12 people. With this, the number of people in each cabin is fixed. But we still don't know how many cabins boys vs. girls use. Insufficient on its own.
Together: Statement 1 gives the cabin ratio (6 boys' cabins for every 5 girls' cabins, using 1.2 = 6/5), and Statement 2 tells us each cabin has exactly 12 people. So boys = 6 * 12 = 72, girls = 5 * 12 = 60, ratio = 72:60 = 6:5.
Answer is C. The key concept being tested is that "ratio of A's cabins to B's cabins" is not the same as "ratio of A to B" unless each cabin holds the same number of people.