—I'm leaving for Canada on a study trip next week.

—_____. [ ]

A. Enjoy your time

B. That's all right

C. You're welcome

D. It's a pleasure

按建筑物层数估算室内给水管网所福的最小压力值的规律是l层建筑物管网压力至少为100Kpa，2层所需最小压力为120Kpa，2层以上每增加一个楼层压力应附加（）Kpa。