(1) A quadrilateral with only one set of parallel opposite sides is called a trapezoid. ( √ )

② Because a trapezoid has four sides, it is a quadrilateral. ( √ )

fill (up) a vacancy

① The isosceles trapezoid has a circumference of 48cm, an area of 96cm2, a height of 8cm and a waist length of (b) cm.

A.24b.12cm C.18cm D.36