Quiz: Perimeter vs Area

A single island has $8$ land cells. You compute its perimeter by checking each land cell's $4$ neighbors and counting water or out-of-bounds boundaries. The perimeter is $12$. If you added $1$ land cell to fill an interior hole, what happens to the perimeter?

1. A.The perimeter increases by $4$
2. B.The perimeter decreases
3. C.The perimeter stays at $12$
4. D.You cannot determine this without seeing the grid