Answer:
B. making food
Step-by-step explanation:
Leaves are essential for the process of making food in the plants as they contain the pigment chlorophyll with the help of which they are able to perform photosynthesis.
Due to this reason leaves are also known as food factory of the plants.
Leaves use sunlight , carbon dioxide, water and chlorophyll to make the food in the form of glucose which can be used by the plants and also releases oxygen into the atmosphere.
In the given , question since Cooper is removing leaves from his potted plant it is the ability of making food which will be affected the most.