Three line segments can form a triangle if the length of the longest segment is greater than the sum of the lengths of the shorter segments.

They can form a triangle.
Now if c is the length of the longest side and a and b are the lengths of the shorter sides, then:
- if

, the triangle is right
- if

, the triangle is acute
- if

, the triangle is obtuse

The triangle is obtuse.
The answer is D.