The correct answer would be - observational approach.
Explanation:
Observation approach is the research technique that involves the observation of the subject or participates behavior in their natural habitat or state. This will be one of best approach to study.
Similarly when characterizing new findings various aspect of experimental, Observational details or modelling approaches will help in identification , classification and nomenclature. However, in comparison to experimental and modeling approach is more appropriate method for the rare endangered species.
Thus, the correct answer would be - observational approach.
