Question

Scuba divers use a red flag with a white diagonal stripe to let other people know the scuba divers are under water. Which angles must be congruent in order for the top and bottom edges of the flag to be parallel?

A) ∠1 and ∠2
B) ∠2 and ∠3
C) ∠3 and ∠4
D) ∠4 and ∠2

Answer 1

the answer is D, because the angles are alternate interior angles  formed by an diagonal

Answer 2

The correct option is D.

Explanation:

If a transversal line intersect two parallel lines then the alternate interior angles are congruent.

It means the top and bottom edges of the flag are parallel if the alternate interior angles are same.

From the given figure it is clear that angle 1 and angle 3 are alternate interior angles. Angle 2 and angle 4 are alternate interior angles.

The top and bottom edges of the flag are parallel if

`\angle 1\cong \angle 3`

`\angle 2\cong \angle 4`

Therefore correct option is D.