VOA慢速英语:加利福尼亚动物园人工孕育的犀牛

artificial insemination – n. a medical process in which male reproductive fluid is used to make a woman or female animal pregnant without sex

species – n.

extinction – n. the state or situation that results when something (such as a plant or animal species) has died out completely

hormone – n. a substance produced in a living organisms and transported in tissue fluids

semen – n. the sticky, whitish liquid that is produced by a male's sex organs

embryo – n. a human or animal in the early part of development