单选题 ______ the employees" working efficiency, the supervisor will allow them to have a coffee break.
【正确答案】 B
【答案解析】[解析] 本题考查不定式。to do可以表示“为了…”，类似词组还有in order to do或so as to do。句意为：为了改善员工的工作效率，老板允许他们有喝咖啡的休息时间。