An interior angle of a regular polygon is 135°. The polygon is a/an:

octagon

sum of interior angles is ( n − 2 ) × 180^∘

interior angle of a polygon = sum of interior angles ÷ number of sides

interior angle of a polygon = ( n − 2 ) × 180^∘/n

135° = ( n − 2 ) × 180^∘/n

( n − 2 ) × 180^∘ = n * 135°

n-2 = n*135/180

 n-2 = 0.75n

0.25n = 2

n = 8

The correct answer is Option (4) → octagon