Taxonomy
brings order to understanding the immense diversity of life
is an unnecessary science
is a classification system
is the study of animal behavior

Option (3)

Explanation:

Taxonomy is usually defined as the classification scheme that is applied to all living organisms, including micro-organisms, plants, and animals. The scientists adopted the hierarchical classification method, which enabled them to study their characteristics and categorize the biological diversities on earth. The organisms are prominently and easily identified by comparing their existing characteristics with the different types of categorized species.

Thus, it is a classification system.

Hence, the correct answer is option (3).