Complete the Figure X from the given alternatives 1, 2, 3, 4

Figure X is a large square divided into four quarters, containing two nested squares and two triangles. Continuing every line into the missing bottom-right quarter: the corners of both inner squares, the slanting line from the left middle point ending at the middle square's bottom-right corner, and the steep line from the small square's top-right corner down to the bottom edge. Only option 4 shows all of these correctly.