You haven't provided neither the diagram nor the options.
Therefore, I cannot provide an exact answer, however, I will try to help you with the concept.
For a triangle, the measure of each angle is proportional to the length of its opposite side.
This means that:
1- The largest angle is the angle opposite to the longest side
2- The smallest angle is the angle opposite to the shortest side
Since you are looking for the largest angle, pick the one facing the longest side
Some tips and tricks:
1- In a right angle triangle, we know that the hypotenuse is the longest side, therefore, the largest angle would be the right angle
2- In an obtuse triangle, the largest angle is simply the obtuse angle itself (the one whose measure is greater than 90)
3- In equilateral triangle, all three angles are equal
Hope this helps :)