<u>Choice A: </u>
<u />
<u>Choice B: </u>9, 40, 41
<u>Choice C: </u>
Answer:
(B)9, 40, 41
Step-by-step explanation:
To check if the sides form a right triangle, you check to see if they satisfy the Pythagorean theorem.

Note that the longest side length is always the hypotenuse.
<u>Choice A: </u>
<u />
Now, 
Therefore:

These side lengths form an equilateral triangle. They do not satisfy the theorem.
<u>Choice B: </u>9, 40, 41
The longest side length is 41.


Therefore:

These side lengths form a right triangle.
<u>Choice C: </u>

Therefore, the longest side length is 

These side lengths do not form a right triangle.