Respuesta :
The best sentence is, Coral reefs are a very important component of the ocean’s ecosystem because they support sea life, such as crabs and sea turtles. It's also the key sentence that explained the whole paragraph. It touched all the topics or supporting details that follow.
The following sentences explained the importance of coral reefs and the need for its protection to save marine life.
The following sentences explained the importance of coral reefs and the need for its protection to save marine life.