Line p is parallel to line q. Which proof explains why the sum of the interior angles of the triangle must be 180⁰?

See proof below

Step-by-step explanation:

Find the diagram attached.

From the diagram, sum of angle on the straight  line l is 180degrees that is:

<A' + <B' + <C' = 180° .... 1

Also note that

<A = <A' (corresponding angle) ...2

<B = <B' (corresponding angle) ... 3

<C = <C' (vertically  opposite angle) ...4

Substitute  2, 3 and 4 into 1, we will have:

A+B+C = 180°

This shows that the sum of the interior angles of the triangle A  B and C is 180°

step-by-step explanation:

it's is b