Dolphins are protected animals. Laws have been passed to keep them from being harmed. But the same laws that help the dolphins can cause problems for fishermen. Fishermen use nets to catch fish for grocery stores and restaurants. Nets make the work go faster, and fishermen catch more fish to sell. It would take a very long time to catch a lot of fish with a fishing pole. The dolphin laws say that fisherman cannot use a certain net anymore because it is dangerous to dolphins. Dolphins are mammals, and they need air to live. If they were to get caught in these nets, they might not be able to swim to the surface to breathe air. Dolphins live in the same areas as big fish. Dolphins often swim and play with schools of tuna. Just like the tuna, they can get caught in the fishermen's nets. Fishermen do not want to catch or harm dolphins. Today, fisherman follow a fishing style using different nets that will not harm dolphins. It is difficult, but the fisherman are careful to only catch tuna and not dolphins. As a result, the dolphin population is growing. What is an example of cause and effect in this passage?

A. There are new laws that are trying to protect dolphins from injury.

B. Dolphins were getting caught in nets because they swim with tuna.

C. Fishermen can catch more fish with a net than with a fishing pole.

D. Fishermen do not mean to hurt dolphins by using fishing nets.