Answer :
Final answer:
The primary structural component at the top end of the rail is known as the Top rail, serving as the uppermost horizontal support in railing systems. so the correct option is 2) Top rail.
Explanation:
The primary structural component at the top end of the rail is called the Top rail. In the context of railing systems or structures, such as fences, balustrades, or handrails, the top rail is the uppermost horizontal member that provides support and stability to the vertical elements, like the balusters or pickets. This term generally refers to the component that caps or completes the assembly that one would hold onto, for instance, when ascending or descending a staircase.
