美国最受欢迎的狗狗品种是什么？

purebred - adj. having parents that are of the same breed

breed - n. a particular kind of dog, cat, horse, etc.

ranking - n. a list of people or things that are ordered according to their quality, ability, size, etc.

passenger - n. a person who is traveling from one place to another in a car, bus, train, ship, airplane, etc., and who is not driving or working on it

baggage - n. the bags, suitcases, and personal things that a person carries when traveling

cesarean section - n. a surgical operation for giving birth in which a cut is made in the mother's body so that the baby can be removed through the opening

registry - n. a book or system for keeping an official list or record of items