Which of the following statements BEST defines vestigial structures? : -Structures that are different in different organisms
-Structures that are still present but currently serve little to no purpose
-Structures that are the same in different organisms
-Structures that are different between the infant and adult forms of an organism

Structures that are still present but currently serve little to no purpose

Explanation:

Vestigial structures/organs are general defined as structures/organs that are present but poorly developed without any functional use in the present living organisms but thought to have been fully developed and functional in their ancestors.

Fully developed and functional organs gradually become less developed and non-functional across generations as the environment keeps changing and organisms found lesser use for the organs. An example includes the caudal vertebrae found in man which is kind of useless but thought to have been fully developed and functional in the ancestors of man - the monkeys.

Vestigial organs are often used as one of the morphological evidence of the evolution of living organisms.

clinically, some people often have repeated allergies, eczema and respiratory infections or other parts of the infection, in this case, in addition to some routine tests such as tests for white blood cells, immunoglobulin series, lymphocyte subsets, etc., the five immune immunoglobulin tests are also necessary.

this is a good question! i'll do some research and come back when i have the answer!