In the diagram, the feature labelled C is only found in plant cells. What is it called?

In the diagram, The cell organelle labeled as c is the chloroplast

The plant cell contains structures that are cell walls, chloroplast, vacuoles that are absent in an animal cell.

Reason:

cell wall present on the outside of the plasma membrane labeled as Evacuoles are the single but largest cellular structure in the plant cell and are present in the center.

Chloroplasts:

The chloroplast is an organelle found in plants and other photosynthetic organisms.The chloroplast contains chlorophyll that gives the plant its green color.Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through photosynthesis.The chloroplasts also have a double outer membrane.  chloroplasts are minute flattened granules.

Thus, In the diagram, The cell organelle labeled as c is the chloroplast