答案B
分析：B项的主句中的动词谓语是一般过去时stopped,而从句中的谓语动词是can have,应该把can have改为could have才对.(延伸)表示“目的”有多种方法,如用for+名词：He stopped for a rest．／I went home for lunch．／The whale comes up for air．用动词不定式：He stopped to have a rest．／To reply to that,you can say something like“Not at all”or“Certainly not”．／He stopped in order to have a rest．／In order to have a rest．he stopped．／He stopped so as to have a rest．(用强化动词不定式表示“目的”的in order to或so as to,in order to可以放在句子的前面或后面,so as to只能放在句子的后面)He stopped so that he could have a rest．／He stopped in order that he could have a rest．(用so that或in order that引出“目的状语从句”,从句中往往有can,could,may,might,从句的时态要和主句保持一致)(延伸)for+名词用来表示“目的”,但for doing不表示“目的”,而是表示“用途”,如：Fire can be used for cooking food．＝Fire can be used to cook food．