Answer:
Photosynthesis. Protists are food producers like plants, they can generate their food by themselves through the process of photosynthesis.
Explanation:
PROTISTS
Protists are eukaryotes that have a nucleus containing their DNA. They possessed membrane-bound organelles, like mitochondria and the endoplasmic reticulum. They are most often than not single-celled, though some are multicellular. The protist kingdom is so diverse because their ways of getting food and reproducing vary widely. They require a moist environment to live so most are aquatic. They can be found in lakes, ocean or damp soil. Some live in or on other organisms while others are free-living. Some protists are more closely related to plants or animals than they are to other protists. Protists are re unicellular as opposed to multicellular plants. Plants are complex and big while protists are microscopic. They are also capable of movement which plants cannot. Protists have complex life cycles. Many have both asexual and sexual reproduction. Examples of protest are; Spirogyra, Euglena, Amoeba, and Paramecium.
Protists can get their food in different ways. They may ingest or engulf smaller particles like bacteria. This is achieved by extending its cell wall around the food item to form vacuole. They may absorb food molecules across their cell wall by process of diffusion. Finally, they can generate their food use in light via photosynthesis.
This process of photosynthesis in which they can generate food like plants makes them suitable for point X in the diagram showing the branches tree for four kingdoms.
