Question

Which of the following cannot be the side lengths of a triangle?

Answer 1

To actually form a triangle, the two SMALLEST sides, have to be bigger than the BIGGEST number, when added together.

A.) Can be a triangle
B.)Can be a triangle
C.)Can be a triangle
D.)Can't be a triangle

2+10=12, and 12 is not bigger than 20. 

Thus, D, is your answer.