undergo,experience,sustain,suffer这些动词均有“经历，经受，遭受”之意。undergoexperiencesustainsufferunderground,subway,tube这些名词均可表示“地铁”之意。undergroundsubwaytubeunderstand,comprehend,appreciate,apprehend,grasp这些动词均有“理解”之意。understandcomprehendappreciateapprehendgraspunfold,open这两个动词均有“打开”之意。unfoldopenunhappy,unfortunate,unlucky,disastrous这些形容词均有“不幸的”之意。unhappyunfortunateunluckydisastrousunwilling,reluctant这两个形容词均有“不情愿的，不愿意的”之意。unwillingreluctantupset,agitate,disturb,perturb这些动词均有“使不安，使心烦意乱”之意。upsetagitatedisturbperturbuse,apply,employ,utilize,avail,exploit这些动词均含“使用，应用”之意。useapplyemployutilizeavailexploitusedto,would这两个词均含“过去惯常，过去总是”之意。usedtowouldusual,customary,habitual,conventional,regular这些形容词均有“通常的，惯常的”之意。usualcustomaryhabitualconventionalregular