I would go with 45,45, 90 because first you can eliminate C and D.
C because it is not an equilateral triangle and D because you can figure it out.
Now you have A and B. A 30, 60 90 Degree Triangle would mean that none of the sides are equal (or the legs don't equal the hypotenuse when you put it in Pythagorean form [a²+b²=c²]). However if you translate the problem to answers that are easier to understand: {(7√3 = 12.124)² + 21² = 587.8944 = 14√3} Then you can see, two angles are equal to each other. So the answer is B.