Please help. I cant figure it out. What shape in this lesson can be used to prove statements about triangles?

circles
triangles
parallelograms
pentagons

Danny draws a transversal, t, on two parallel lines ab and cd, as shown below: he makes the following table to prove that the alternate interior angles are equal: which is the missing justification? (6 points) corresponding angles formed by a transversal on parallel lines are supplementary. corresponding angles formed by a transversal on parallel lines are congruent. co-interior angles formed by a transversal on parallel lines are congruent. co-exterior angles formed by a transversal on parallel lines are congruent.

Need on this one asap im almost done with this subject

What is the volume of a cone with a height of 6 cm in the radius of 2 cm