Explanation:

Only statements 1&3 are correct.

• Halteria — microscopic ciliates (a single-celled organism with minuscule hairs) that populate freshwater worldwide — can thrive wholly on a virus-only diet or ‘virovory’.

• Halteria plankton are found in large numbers in freshwater bodies.

• They are heterotrophs meaning they can’t produce their own food.

• Plankton are usually microscopic, often less than one inch in length, but they also include larger species like some crustaceans and jellyfish.

• Scientists classify plankton in several ways, including by size, type, and how long they spend drifting.

• But the most basic categories divide plankton into two groups: phytoplankton (plants) and zooplankton (animals).

• Phytoplankton are microscopic plants, but they play a huge role in the marine food web.

• Like plants on land, phytoplankton perform photosynthesis to convert the sun’s rays into energy to support them, and they take in carbon dioxide and produce oxygen.

• Zooplankton include microscopic animals (krill, sea snails, pelagic worms, etc.), the young of larger invertebrates and fish, and weak swimmers like jellyfish.

Hence option 3rd is correct.