The correct answers are:
90°, 180° and 270°
Step-by-step explanation:
Squares have rotational symmetry at 90°. This can be found by dividing the number of degrees in a circle, 360, by the number of sides, 4:
360/4 = 90
This means that at all multiples of 90, the square will rotate onto itself. This means that 90, 180 and 270 are all correct.