Explanation:
The answer is b. an obtuse. This is because if it were a right-angled triangle, then 90 + 30 + 40 would equal 180 and it doesn't. It's obtuse because 30 + 40 = 70, and triangles have to add up to 180° so the last angle would need to be 110°, which is an obtuse angle. I hope this helps!