题目内容：
根据以下材料，回答题Sea Horses
Sea horses are unusual parents. The female sea horses lay the eggs, but unlike other creatures,it's the males that give birth to the young.
Male sea horses have a fold of skin on their bellies that forms pocket, called a brood pouch.
During the breeding season, the sea horse's pouch swells to receive eggs. A female sea horse lays up to 200 eggs at a time in the pouch. Then she swims off, leaving her male partner to care for the developing eggs and give birth to young sea horses. The female will return everyday to check on her mate and the eggs, but she doesn't stay long, nor does she take part in the birth.
It takes from two to six weeks for the eggs in the male's pouch to develop. During this time the male avoids open water and hides in sea grass. His big pouch makes it difficult for him to swim, so the male often uses his tail to grasp a piece of sea grass. Firmly gripping the grass, he will stay perfectly still for hours or even days. The male sea horse will change his color to blend with his surroundings and avoid being seen by predators who will try to eat him or poke holes in his pouch to get the eggs.
The eggs hatch inside the male's pouch. When the babies begin moving around, the male sea horse knows it's time for them to be born. He grabs a sea grass stem with his tail and begins rocking, bending, and stretching his body so that the rest of the babies can be born. Sometimes he has to press his pouch against a rock or some stiff seaweed to force the young out.
Sea horse babies are bom in groups of five or more. Sometimes it takes two days for the father sea horse to give birth to all his young. He is very tired when it's over.
Soon after giving birth to one brood, the male will approach his mate and show her his empty pouch. This tells her he is ready to receive eggs again.
What part does the female sea horse play in having babies? A．Receiving eggs.
B．Laying eggs.
C．Hatching eggs.
D．Protecting eggs.
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