Carlos calculated the missing side length of one of these triangles using the pythagorean theorem. which triangle is it?

four triangles a, b, c, d are shown from left to right. triangle a has a side labeled as 2 and another side labeled as 3, and the included right angle is shown. triangle b has one side labeled as 3 and the other as 6 and the included obtuse angle is shown. triangle c has one side labeled as 2 and the other also as 2 and the included acute angle is shown. triangle d has one side labeled as 4 and the other as 3, and the included obtuse angle is shown.

a
b
c
d