文化背景知识注释的理解 — 英语选择题

北师大版七年级上册《Notes to the Texts》的文化注释提到：英式英语中 ground floor 指我国常说的一楼，first floor 指我国的二楼。英国学生 Lily 在伦敦一栋楼的三层上课（按我国习惯的楼层计算），她应该对同学说： A. My classroom is on the second floor. B. My classroom is on the third floor. C. My classroom is on the ground floor. D. My classroom is on the first floor.