What do you call a polygon with 3 sides and 3 angles?

How many diagonals does a triangle have?

Which of the following is a 3-sided polygon?

What polygon has 4 sides and 4 angles?

Is a square a rectangle? 

Which of the following is a four-sided polygon?

Is a square always a rhombus? 

Is rhombus a trapezoid?

What kind of quadrilateral has four equal sides and four right angles?

What kind of quadrilateral has only one pair of parallel side?