雅思写作必备同义词 puzzle, bewilder, perplex, baffle rule, regulation key crucial, critical supply, provide, afford conserve, preserve assure, ensure, guarantee, pledge, change, alter, modify convert into, often, frequent, constant allege, assert, declare, claim express, voice, utter, pronounce happen, occur, take place cost, expense, expenditure deny, negate buy, purchase appraise, assess, evaluate, estimate encourage, embolden, hearten, inspire attribute, ascribe, credit, impute, abundant, copious, profuse, ample reason, factor, cause bad, baneful, evil, harmful, detrimental development, advance ,progress useful, helpful, beneficial, profitable, rewarding important, critical, essential result in, bring about, give rise to, lead to, cause