Answer :
Chloroplasts. They are only in green plant cells, so, unless you are a green plant, humans and flatworms would not contain them.
The following structures does a fern have, but a flatworm and a human don't is the chloroplasts.
What is the function of the chloroplast?
In the chloroplasts, the reaction of the most fundamental importance for the life of plants and, indirectly, for the life of animals takes place, photosynthesis. Chloroplasts are usually discoidal and their color is green due to the presence of a pigment called chlorophyll.
Chloroplasts are organelles that occur only in plant and algae cells and are rich in chlorophyll, a green coloring pigment. They are related to the process of photosynthesis and, in plants, they are mainly found in leaves.
See more about chloroplasts at brainly.com/question/11136550?
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