Context: Below is a food web from Little Rock Lake, a freshwater lake ecosystem in Wisconsin.
A food web models how the matter eaten by organisms moves through an ecosystem. The arrows in a food web represent how matter moves between organisms in an ecosystem.
Which of the following organisms is the omnivore in this food web?
A. rotifer
B. golden algae
C. green algae
Pick the correct answer from the listed options and provide the letter of the selected option.

A