A 3x3 grid is presented. The top row contains: [A square with a small black circle in the top-left corner], [A square with a small black circle in the top-right corner], [A square with a small black circle in the bottom-right corner]. The middle row contains: [A triangle with a small black circle in the top-left corner], [A triangle with a small black circle in the top-right corner], [A triangle with a small black circle in the bottom-right corner]. The bottom row contains: [A circle with a small black circle in the top-left corner], [A circle with a small black circle in the top-right corner], [A missing square]. Which of the options below completes the grid?