(03.01 lc)

in triangle stu, u2 = s2 + t2.
which equation is true about the measure of the angles of the triangle?

the measure of angle stu is equal to 100 degrees
the measure of angle sut is equal to 90 degrees
the measure of angle stu plus the measure of angle tsu is equal to 80 degrees
the measure of angle stu plus the measure of angle tsu is equal to 70 degrees