I'm so sorry if it's wrong I took geo last year online and I still hated proofs. Transitive property is basically when x=y, y=z so x=z. since <4 and <5 are congruent and <1 and <4 are congruent, that would make <1 and <5 congruent because of the transitive property. Good luck with proofs!
The points of a line can be put into one-to-one correspondence with the real numbers so that the distance between any two points is the absolute value of the <span>difference</span>of the corresponding numbers. So the answer is B.