Answer: They all survive in any environment.
Explanation: Protists have the ability to survive in any environment, even extreme environment. They can live in the ocean, desert or extremely hot environment, or even a extremely cold environment.
I'll explain why the others aren't correct.
Protists can be both unicellular and multicellular, they're not always unicellular. Kingdom Protista contains all eukaryotics, so they're not always unicelluar.
Protist cannot make or consume food. Animals consume food, and plants make food, not protista. Yes they're many plant-like protists out there, such as algae, they get their food from the sun above. So all protists cannot make or consume food.
Protist does have flagella, but not all protists. Protists that are motile and generate movement have flagella, meaning they move. Not all protist move, like plants can't move. So, not all protists have flagella, meaning they can move.
Let me know if you have any questions.
<em> Sincerely, Lily :)</em>