Step 1: Understanding Heap Properties.
- **Parent(i)**: We can compute the parent of node \( i \) using the formula \( \text{parent}(i) = \frac{i-1}{2} \), which gives the index of the parent node in a binary heap.
- **Left(i)**: We can compute the left child of node \( i \) using the formula \( \text{left}(i) = 2i + 1 \).
- **Right(i)**: We can compute the right child of node \( i \) using the formula \( \text{right}(i) = 2i + 2 \).
Step 2: Heap Size.
We cannot compute the heap size directly from the index of a node. The heap size is generally known from external information or passed along with the heap structure.
Step 3: Conclusion.
Thus, the correct answer is **(2) Heap size**.