D. Side Length of 4 in, 8 in and 12 in This is because of a theorem(Theorem- a statement that can be proven) called Triangle Side Theorem. In this statement, 2 side of a triangle has to be bigger than one side. In this problem 4+8=12 is not greater than 12. Therefore meaning D doesn’t produce a triangle.
You mean a square has an AREA of 100 square meters? The length of 1 side equals square root of 100 = 10 meters. Therefore perimeter = 4 * 10 = 40 meters.