根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。
Some animals can be trained to help humans. For example, specially trained dogs help blind people walk around the town safely. Some kinds of monkeys can be taught things too.     The monkeys pick up the phone when it rings, carry shopping bags and do housework.
In the wild, animals and humans are not usually friends.    In Africa, the honey- guide bird works with humans to find food. The bird likes to eat the grubs (幼虫) — a type of insect that lives inside a beehive (蜂巢). It knows how to find beehives but it can’t open them and get the grubs. People like to eat honey, but they aren’t very good at finding beehives.       The bird flies to a beehive and people follow it. When the people open the beehive and take the honey, they give the grubs to the bird.
In Laguna in the south of Brazil, fishermen and dolphins work as a team. The ocean isn’t very clean, so the fishermen can’t see the fish.      When the dolphins find a large group of fish, they make a noise to tell the fishermen. Then the dolphins push the fish to the beach. The fishermen wait in the water near the beach and catch a lot of fish in their nets. The fishermen’s nets make it easier for the dolphins to catch fish too. In Laguna, fishermen and dolphins have been working together for many years.   Meanwhile, the dolphins must be happy to help because they teach their babies how to work with the humans!

A．They attack each other for food or something else.

B．So the bird and the people help each other.

C．They can learn how to help people who can’t use their arms or legs.

D．In fact, they usually help to get enough food for their babies.

E. The fishermen teach their children how to work with the dolphins.
F. However, there are a few interesting examples where they can work together.
G. However, dolphins can find them easily by using sounds.