Question

Triangle ABC is an obtuse triangle with the obtuse angle at vertex B. Angle A must be

less than 90°
greater than 90°.
congruent to angle B.
congruent to angle C.

Answer 1

An obtuse triangle has all different measurements, which leaves your last two answers out.

If the angle at vertex B is obtuse, that means that the other two angles has got to be less than 90 degrees, because a triangle is 180 degrees, and your angles can't be more than 90 otherwise, you won't have a triangle.

Your answer is less than 90 degrees.

Hope this helps ;)