Hello there! :D
First of all, let me put in a picture of a food web for you to reference!
(you should see it below)
Let's talk about how a food web works. Many science books will tell you that a food web is like a pyramid, but this could not be more false! A food web shows the relationship between consumers and producers within any given ecosystem. Sometimes it is not as simple as a line or diagram, because some animals can be both primary, secondary, and teriatry consumers (us!!).
Look at the food web below, and see the grass that eventually is eaten by the grasshopper. We know that the primary source of energy for plants is the sun, which is not included in the web, but just so you know for reference for future questions. What thing in this web supplies the energy for the entire food chain? The producers! This would be the grass and the planktin you see in the web.
What is the difference between primary and secondary consumers?
Glad you asked! Primary means first, and secondary means second. Primary consumers are cosumers that directly eat producers. That would be the grasshopper or the fish! Secondary consumers recieve energy from producers from primary consumers. Examples of these are the mouse and lobster.
So, the best answer to the question above is a Herbivore that feeds on producers, because a primary consumer is a consumer that eats producers directly, and most producers are plants! Answer "B".
I hope this helps you and you have a wonderful day,
Kai xx