企业物流管理既不能单纯追求单个物流功能的最优，也不能片面追求各“局部物流”最优，而应实现企业整体最优。( )

Travel can not only relax us from the pressure of work for a while but ____ our knowledge of the world. [ ]

A. bring out

B. add to

C. add up to

D. increase to