Choose the rectangle.
We’re given five different shapes. We have to choose the one which is a rectangle. Let’s think about what we already know about rectangles. A rectangle has four sides. Which of our five shapes has four sides? A circle doesn’t have any sides. This shape has three sides; it’s a triangle. So we have three shapes left to choose from.
Each of these shapes has four sides. But we’re only looking for one rectangle. What else do we know about rectangles? Rectangles also have four right angles. Each of its four angles is 90 degrees. The first of our shapes has four right angles. None of our other shapes with four sides have any right angles. This is the rectangle. It has four sides and four right angles.