The boy sat. That could be a subject. The predicate is the half-sentence you have right now. So, it could be The boy sat in the window seat on the plane.
Explanation:
A subject contains the noun. A predicate contains what the noun does.
The answer is c. The problem is basically asking which of the answers is greater than 11,987 but less than 12,014. Out of those answers 12,001 fits the description