What may be the cause of drug resistance? ( )

参考解析：

根据文章第八段drug-resistant HIV might develop when people interrupt treatment可知当中断治疗的时候耐药性会加强，选项B表述正确。根据首段drug resistance against two drugs that constitute the backbone of HIV treatment: efavirenz and nevirapine.可知选项A提到的两种药物正是患者产生耐药性的药品，不是原因。根据倒数第三段People living with HIV might go on and off the drugs for several reasons…Drug shortages at clinics could also contribute可知药品短缺是间歇性吃药的原因之一，而非产生耐药性原因，选项C表述错误。根据文章末段If treatment delivery is poor or patchy, resistance could emerge.可知当实施治疗断断续续或者不理想，耐药性会出现，这说明耐药性的产生源自于实施治疗的断断续续，所以选项D不是原因。故本题正确答案选B。