Hey there! I'm happy to help!
When looking for a conclusion, we have to find something that we can figure out from the information but they don't directly tell us.
Answer B says that a conclusion is that the lines meet at a 90 degree angle, but they already told us that, so this is wrong.
Answer C does the same thing, so it is wrong as well.
A 90 degree angle is a right angle. They already told us that the lines intersect at a right angle, so this is not a conclusion.
Answer A says that the lines are perpendicular. They don't directly tell us that these specific lines are perpendicular, but from the information they gave us we can figure it out. Therefore, the correct answer is A. The lines are perpendicular.
Have a wonderful day! :D