-Can you go swimming with us this afternoon?-I’d like to, but I ________ take care of my little sister at home because my mother is ill．A.needB.mustC.shouldD.have to
网友回答
D解析此题考查情态动词的用法．need表“需要”．作情态动词常用于疑问句或否定句中．should表“应该”，must或have to表“不得不，必须”．根据句意应用must或have to．又因为must表客观，have to表主观，根据“妈妈病了”，所以选D．