Question

In a geometry class, the students were asked to prove the theorem below by contradiction.

Theorem: A quadrilateral cannot have three and only three right angles.

Heather begins the proof with an assumption. Which statement will she most likely use as an assumption?

Let one angle of a quadrilateral be acute and the other three angles obtuse.

Let all angles of a quadrilateral measure 90° each.

Let all angles of a quadrilateral be acute.

Let one angle of a quadrilateral be obtuse and the other three angles measure 90° each.

Answer 1

proof by contradiction starts by assuming that the opposite is true - that in this case a quadrilateral has only three right angles.
the last option is most likely