观察下面的算式：

5×9=45

55×99=5445

555×999=554445

5555×9999=55544445

则555555×999999=（　　）

    Careers in zoology are extremely varied and unique, and can provide incredible learning and work opportunities for anyone devoted to animal studies and welfare. Zoology, or the study of animals, is a wide field with many specialties, including research, conservation, veterinary (兽医的) medicine, and the care of animals. For people with a love of animals and some training, dreams of careers in zoology may come true.

    Some careers in zoology focus on research and scientific studies. These careers may allow those with a good theoretical science background to develop and run studies that improve human understanding of the animal world. Research in zoology can help create safer and more effective products for animals or can teach humans more about animal behavior in order to aid in conservation, breeding programs, and habitat preservation.

    Careers in zoology that focus on conservation attach great importance to the continued survival and increased protection of animal species. Conservationists may work with political groups or governments to help make laws to protect and preserve animals, or may work in the field gathering information on potential threats to the health of global ecosystems. Some conservationists work in educational fields, trying to improve human efforts to save animals from extinction.

    Animals are subject to illness and injury, and some careers in zoology help to create a safe, stable animal population. Veterinary medicine is an important specialty field, and may take several years of intensive training to qualify as a certified veterinarian. While many veterinarians focus on the small-animal practice of domestic pets, vets in rural areas often work with large farm animals and more adventurous veterinarians may work with exotic species in zoos and wildlife preserves. .

    Humans love to observe animals, and modern-day zoos and wildlife preserves help meet that interest while providing facilities to assist with conservation programs. Zoology careers in zoos can range from overseeing breeding programs, to creating the proper diet for a deer, to cleaning the tiger's cage. Many volunteer and entry-level jobs are available for people that love animals.

已知D（x₀，y₀）为圆O：x²+y²=12上一点，E（x₀，0），动点P满足 $\overrightarrow{OP}$ = $\frac{1}{2}\overrightarrow{ED}$ + $\frac{\sqrt{3}}{3}\overrightarrow{OE}$ ，设动点P的轨迹为曲线C．