Homologous structures can be best be described as structures

are so similar that they imply a common ancestor

have the same structures and functions

have the same structures

had a function in an ancestor but don't have that function today

Homologous structures can be best be described as structures that are are so similar that they imply a common ancestor.

Option A

Explanation:

In evolution a number of organisms have lost some of their structures and a number of organisms have gained some of their structures for their survival. According to Darwin , the most fittest organism has survived.

For exhibiting this many organisms have attained several modifications. So when we look into homologous structures in 2 different species we can thereby relate and tell that they are from a common ancestor.