1、Words ReviewRead the explanation and speak out the word it explains.based on chance rather than being planned or based on reason to get sth., especially by asking for it, buying it, working for it or producing it from sth. else an important discovery or event that helps to improve a situation or pro
2、vide an answer to a problem breakthroughn. 突破proceduren. 程序；步骤；手续obtain vt. 获得；赢得arbitraryadj. 任意的 a set of actions which is the official or accepted way of doing sth. a change made to sth. in order to correct or improve it, or when you make such a change to do or begin to do sth., especially sth. t
3、hat will take a long time or be difficult commercialadj. 商业的；贸易的undertakevt. 着手；从事；承担mediumn. 媒介；手段；工具related to buying and selling things a method or way of expressing sth.correction n. 改正；纠正； 修正objectionn. 不赞成；反对；异议accumulatevt. to achieve forbidvt. 禁止；不准attainadj. 成对的；成双的 twineither of two children born to the same mother on the same occasionto refuse to allow sth., especially officially, or to prevent a particular plan of action by making it impossible n. 双胞胎之一；孪生儿之一
