Answer:
C.
14 cm, 6 cm, 18 cm
Step-by-step explanation:
According to the Triangle Inequality Theorem, the sum of any two sides must be greater than the third side.
To test this with each of your choices, add your two smaller sides together and see if they are greater in length than your largest side.
[tex]9+12>25\\21>25[/tex]
21 is not greater than 25, so it is not answer choice A.
[tex]12 + 21 > 34\\33 > 34[/tex]
33 is not greater than 34, so it is not answer choice B.
[tex]6+14>18\\20>18[/tex]
20 is greater than 18, so answer choice C is correct.
[tex]30+31>63\\61>63[/tex]
61 is not greater than 63, so it is not answer choice D.
