根据下面资料，回答题 Almosteveryonesuffersfromaheadache21(occasional).Butsomepeoplesufferfromrepeated,frequentheadaches. WhatisheadacheWhatcausesitWhatcanyoudoaboutaheadacheWhatresearchisbeingdoneonheadachesThedictionarydefinesheadachesimply22"apaininthehead".23mostpeoplemeanbyheadache24(be)apainthatlastsseveralminutesorhours.Itcoversthewholehead,oronesideofit,orperhapsthefrontorthebackofthehead.Toaddtotheconfusionaboutadefinition,somepeoplecalltightfeelingintheheadaheadache. Aheadacheisimportantbecause25canbethefirstwarningofaseriousconditionwhichprobablycouldbecontrolled26discoveredearly.Ifaperson27(remove)thewarning,dayafterday,withapain-killer,hemaypassthepointofeasycontrol. Aheadacheisimportantalsobecauseitdisturbspeople,28(prevent)themfromlivingahappylife.The29(employ)withaheadachedoeslesswork.Inaflashoftemperhemayupsethisfellow30(guy)orcustomers,causingadirectorindirectlosstohisorganization.Themotherwithaheadachesuffersanddisturbsthefamily.Sheupsetsherhusbandandchildren.
preventing。解析：考查非谓语动词。在because引导的从句中已有谓语动词，这里要用非谓语动词形式。该动词表示的动作与前面的主语it构成逻辑上的主谓关系，故用其现在分词形式preventing。
