Step-by-step explanation:
it clearly says (and also shows it by specifying 4cm × 4cm side lengths) : a square base.
so, all net diagrams not having a square in the middle (but a rectangle or a triangle) are out.
and in fact, all 3 that have a square in the middle, are valid nets that would fold up to the pyramid : the 2nd, 4th and 6th.
