A quadrilateral ABCD is a trapezium, if :

1. AB = DC

2. AD = BC

3. ∠A + ∠C = 180°

4. ∠B + ∠C = 180°

If the diagonals of a square ABCD intersect each other at point O, the triangle OAB is :

1. an equilateral triangle.

2. a right-angled but not an isosceles triangle.

3. an isosceles but not a right-angled triangle.

4. an isosceles right-angled triangle.

Which of the following is not true for a parallelogram :

1. opposite sides are equal

2. opposite angles are equal

3. opposite angles are bisected by the diagonals

4. diagonals bisect each other

If the diagonals of a quadrilateral bisect each other at right angle, the quadrilateral is :

1. square

2. rhombus

3. parallelogram

4. rectangle