Hxen.com's tips：Every day persisted can learn English well!-->■Learn English Everyday■
tick – v. to mark (something) with a written tick or check
diabetes -- n. medical: a serious disease in which the body cannot properly control the amount of sugar in your blood because it does not have enough insulin
imperfect – adj. having mistakes or problems : not perfect
plexiglass – n. a clear plastic often used in place of glass
shield – n. something that defends or protects someone or something
elf -- n. a small creature in stories usually with pointed ears and magical powers
interaction – n. the act of talking or doing things with other people
