Which of the following statements is true 1.congruent angles are always 45º. 2.congruent angles are always supplementary. 3.congruent angles are always complementary. 4.congruent angles have the same measure.

Hello There!

The first statement is incorrect as congruent angles have the same measure but it doesn't have to 45°. It can be any value.
The second one is also incorrect. Congruent angles have the same measure but don't always total to 180° (which is what supplementary means). It would only be true if they are congruent right angles.
The third one is also incorrect as they don't always total to 90° either (Which is what complementary means). 
The fourth one is correct, this is because congruent angles are simply angles with the same measure.

In short, you're answer is 4. Congruent angles always have the same measure. 

Hope This Helps You!
Good Luck :) 

Hey, can you post the problem?