Assertion $(A)$: Among group $13$ elements, boron's melting point is unusually high $(2453 \mathrm{~K})$.
Reason $(R):$ Solid boron has a strong crystalline lattice.
In the context of the above statements, choose the correct answer from the following options:
- ABoth $A$ and $R$ are true, but $R$ is not the correct explanation of $A.$
- ✓Both $A$ and $R$ are true, but $R$ is the correct explanation of $A.$
- C$A $ is true, but $R$ is false
- D$A$ is false, but $R$ is true
