Unfortunately you did not introduce the organisms identified in part B, as the question shows. This makes it impossible for me to answer this question, but I will try and help as best I can.
In the figure attached to the question below, it is possible to see an example of a food web and the arrows that indicate the direction of the energy flow within this food web.
In this sense, we can determine that a food web is the set of food chains that complete and mix. A food chain shows how living organisms organize themselves so that one feeds on the other, whereas in the food web, this food chain is shown in a more realistic way, as it shows how food chains mix and interact within the ecosystem, as they do not there are food chains isolated in nature.