5.19 List4 part2

needed for a particular purpose adj. 必须品，需要的，n. 必需品

to bring food that you have alreadly swallowed back into your mouth v. 使涌回，喷回，流回

if liquid,gas etc.permeates something,it enters it and spread through every part of it v.弥漫，渗透，普及

any cold-blooded vertebrate of class reptitilia including tortoises,turtlrs,snakes,lizards,alligators,crocodiles and extinct forms n.爬行动物 adj,爬虫类的

to give a flower or plant pollen so that it can produce seeds v.给...授粉

an event resulting in great loss and misfortune n. 大灾难 ，大祸

having or expressing more than one possible meaning,sometimes intentionally n.不明确，含糊，暧昧，模凌两可

to completely get rid of something that is necessary or unwanted v. 除去，排除，剔除

a force that moves something along n.动力，推动力