C is an ellipse. Idea: The shadow of a circle is an ellipse, and the shadow of an ellipse is a circle with a specific angle.
B is an incomplete ellipse. The idea is the same as C (the incomplete part is a straight line).
I just made a mistake. My memory is confused.
The inclination angle is ellipse when it is less than the bus, hyperbola when it is greater than the bus and parabola when it is equal to the bus.
As far as the fourth grade of primary school is concerned, it cannot be analyzed as hyperbola, but as the vertex is smooth (as mentioned earlier) and the vertex of triangle is pointed.