Question

scientists estimate there to be how approximately how many different species of nematodes?
1,000,000
20,000
9,000
4,500

Explanation:

Nematodes (roundworms) have an estimated number of species. Scientific estimates suggest that there are approximately 1,000,000 species of nematodes (though many are yet to be discovered and described formally, and the known described species are far fewer, but the estimated total diversity is around a million). The other options (20,000, 9,000, 4,500) are too low as they represent more of the described species count rather than the estimated total.

Answer:

A. 1,000,000