What shape best describes the cross-section cut at an angle to the base of a right rectangular prism? Trapezoid Parallelogram Square Rectangle

Ihave trouble finding the nth term of a linear sequence

If the altitude is drawn to the hypotenuse of a right triangle, then the two triangles formed are similar to the original triangle and to each other. which set of triangles shows the similar triangles created by the altitude in the diagram?

What rotation was applied to triangle def to create d’e’f’?