Hxen.com's tips：Every day persisted can learn English well!-->■Learn English Everyday■
vertebrate – n. animal with a backbone
lens – n. the clear part of the eye that focuses light to see images
determination – n. finding out or calculating something
magnitude – n. the size or importance of something
longevity – n. the length of life
metabolism – n. the process that a living thing makes food and water into energy
