Final answer:
A crab is classified as a consumer since it feeds on other organisms for energy, unlike tulips, giant kelp, and green algae, which are producers that perform photosynthesis to create their own food.
Step-by-step explanation:
The organism classified as a consumer from the given options is c. Crab. Consumers are organisms that depend on other organisms for their food and are also known as heterotrophs. They cannot produce their own food through photosynthesis like producers do. Instead, they obtain energy by consuming other organisms or organic matter. For instance, a tuna is a tertiary consumer, a sculpin is a secondary consumer, and an urchin is a primary consumer.
In contrast, tulips, giant kelp, and green algae all perform photosynthesis and are thus classified as producers. Giant kelp, for example, is a type of multicellular brown algae that, like green algae and red algae, produces its own food through photosynthesis. Therefore, while the crab is the only consumer among the options provided, tulips, giant kelp, and green algae are classified within other roles in the ecosystem.