The Solution:
Given the lengths below:
![10\operatorname{cm},\text{ 12cm, and 20cm}]()
We are required to investigate whether the lengths given above can be the sides lengths of a triangle.
Step 1:
We shall apply the Triangle Inequality Theorem.
This theorem states that if the side lengths of a triangle are a, b and c, then the following holds:

In this case,
Step 2:
Applying the triangle inequality theorem, we have



Thus, we shall conclude that it is possible for the given lengths to be side-lengths of a triangle since the set of lengths satisfies the triangle inequality theorem.
Therefore, the correct answer is: Yes, it is possible for the given set of lengths to be the sides of a triangle.