Me & explain i appreciate it: )

Let's start with what is true. It's B. You need 2 facts to prove that lines are perpendicular when parallel lines with a transversal is involved.

1. You need the The line you want to perpendicular to the transversal and the transversal to form supplementary angles.

2 You want the supplementary angles formed to be equal.

Condition 1 has been met by the fourth step. So it must be condition 2 that you need in step 3. <AFD = <AFE Reason Two angles that are equal to the same angle must themselves be equal.

Now the question becomes why not the others?

A is true, but unnecessary. You are going to end up proving that BC is perpendicular to GH which is not what you want.

C is also true, but you will again end up with an unnecessary step. Where do you go from there?

D You can prove that, but it's going to make the question much longer.

i think it is 18

step-by-step explanation: