1, divergent thinking, two circles, two triangles and two straight lines can spell out many patterns, and can spell out two chandeliers, snowmen, two street lamps and other graphics.

2. In the plane, a closed curve formed by a moving point rotating around a certain point is called a circle.

3. Triangle is a closed figure composed of three line segments on the same plane but not on the same straight line, which has applications in mathematics and architecture.

4. A straight line consists of countless points. A straight line is a part of a surface and then constitutes a body. There is no end point, extending to both ends indefinitely, and the length cannot be measured.