An obtuse triangle has ONLY one greater-than-180 angle measure, so this fact rules out B. An equilateral triangle has 3 exact same sides and an isosceles triangle has 2 equal side lengths. Since the "tally marks" is all different, this mean it's neither equilateral nor isosceles, so this fact also rules out A and D. Since a scalene triangle has no equal side length, and the only option available is C. SO THE FINAL ANSWER IS C
