Answer is C. 12, 13, 20
This deals with the Triangle inequality theorem. This states that the two shortest sides ,when added together, must be greater than the largest side.
12 + 13 = 25 , which is greater than 20.
The others could not work:
A. 3 + 6 = 9 which is equal to 9
B= 5 + 5 = 10 which is less than 11
D. 6 + 7 = 13 which is equal to 13
