Acoupleofweeksago，mydadhadatotalkneereplacementoperationonhisleftknee．Laterinhisward，hewaslaughingashetoldthestoryofhearingthehammerandsaw （锯） astheytookoutthebone．Withasmileonhisface，headvisedthedoctorstosharpenthesaw，sincehecouldsmelltheboneburningastheyremovedit．

Hecamehomeanddidtheexercisesthedoctorshadgivenhimandevenwhenithurthemanagedtomakejokesaboutthenewmetalkneebeingheavier，whichmadeithardertolift，buthedidlift，bendandmoveitanyway．

Yesterday，IwenttovisitmyparentsandwastoldbyMomthathewasintheroomforkeepinghistools．Iwalkedintotheroomtofindhimsittingonthebenchlaughing．Iaskedwhatonearthhewasdoing．Heexplainedthatsincesomethingwentwrongwithhiswalker （助行架） hewaschangingthelegsofit．ItseemedthatMom'swalker，whichshehadusedfiveyearsago，wasbrokenonthetop，butthelegswereingoodcondition．Thoselegswouldn'tfitandhecouldn'tgetofftheonehehadchangedsohecouldn'tgetback．

Together，mydad，withtheuselessknee，andI，withthecrippled （残废的） armsandhands，workedandworkedlaughingallthewhile．Themoretroublewehad，theharderwelaughed．Wedidfinallygetthewalkerfixedandgotback．Tiredandfeelingthephysicalpain，wehadcreatedawonderfulheart-warmingmemory．Ihavebeenfortunateenoughtohavemanysuchminuteswithmydad．

21．WhichofthefollowingcanNOTdescribethecharacteroftheauthor'sfather？___

A．Humorous． B．Stubborn．

C．Optimistic． D．Strong-willed．

22．Accordingtothepassagewecaninferthat___．

A．thethreepeopleinthefamilyallhavephysicalproblems．

B．thefathercomplainedaboutthepainindoingtheexercises．

C．themotherrefusedtoofferhelptothefatherintrouble．

D．theauthordoesn'tlikejokingwithpeople．

23．Whichcanbeasuitabletitleforthetext？___

A．MyDad'sKnee

B．LaughingwithMyDad

C．BeingDisabled

D．WalkerinNeed．