Solution:
As per the problem we have
A right isosceles triangle has an angle with a measure of 45 degrees.
As the triangle is right isosceles, it mean one of the angle will be 90 degree and the rest of the two angles will be equal.
As we know the sum of the angles of a Triangle is always 180 degrees.
Hence the third angle of the Right isosceles triangle will be 45 degrees.
Hence the correct option is B.