Introduction
Species are a fundamental concept in biology and are crucial for understanding the diversity of life on earth. Taxonomists, scientists who classify organisms, use the concept of species to group organisms based on their shared characteristics. There is ongoing debate about the exact definition of a species and how to determine them.

Real basic units of classification
Species are considered as the real basic units of classification. This is because they represent the smallest group of organisms that share common characteristics and can interbreed to produce viable offspring. Taxonomists use species as the basis for higher levels of classification, such as genera, families, and orders.

Lowest unit of classification
Species are also considered the lowest unit of classification. Taxonomists use a variety of characteristics to determine species, including physical characteristics, genetic information, and behavior. The process of identifying and defining species can be complex and challenging, especially for organisms that reproduce asexually or have hybridization events.

Artificial concept of human mind which cannot be defined in absolute terms
Some scientists argue that the concept of species is an artificial construct created by humans and cannot be defined in absolute terms. They point out that many organisms have complex life cycles or hybridization events that make it difficult to determine where one species ends and another begins. In these cases, the concept of species may not accurately reflect the biological reality.

Real unit of classification devised by taxonomists
Despite ongoing debate about the exact definition of species, taxonomists continue to use this concept as a real unit of classification. Species are a fundamental building block for understanding the diversity of life on earth and are essential for conservation efforts. By understanding the relationships between different species, scientists can develop strategies to protect biodiversity and promote the health of ecosystems.

Species are real basic units ofClassification. Species are defined as the group of natural population whose members can interbreed among themselves and are reproductively isloated from other such groups. Hence opt A is correct