Explanation:

Statement 1 and 4: Protozoa is an informal term for single-celled eukaryotic organisms, either free-living or parasitic, which feed on organic matter such as other microorganisms or organic tissues and debris.
Historically, the protozoa were regarded as "one-celled animals," because they often possess animal-like behaviors, such as motility and predation, and lack a cell wall, as found in plants and many algae.
Statement 2: Free-living protozoans are common and often abundant in fresh, brackish and salt water, as well as other moist environments, such as soils and mosses. Some species thrive in extreme environments such as hot springs and hypersaline lakes and lagoons.
Statement 3: Protozoa, as traditionally defined, range in size from as little as 1 micrometre to several millimetres, or more.
Among the largest are the deep-sea–dwelling xenophyophores, single-celled foraminifera whose shells can reach 20 cm in diameter.
All protozoa require a moist habitat; however, some can survive for long periods of time in dry environments, by forming resting cysts which enable them to remain dormant until conditions improve.