The correct option is D 2 million
Life on Earth has been evolving for more than 3000 million years. It continues to do so. It has been estimated that the total number of species of plants and animals living today varies from 5 to 5 million, but only 1.8 million species have so far been described. Of the total known biodiversity, about 0.5 million species represent plants and the remaining species contribute animals. This huge variety of living things reflects the geological, climatic and other environmental differences that occur on this planet. These species live together as ecological communities, some are producers, others are consumers. Each is dependent on the presence of many other species.