京津冀所在的华北地区，水资源短缺的原因与下列哪些因素有关

①土地和耕地面积大；②人口少；③水资源利用率高；④水资源总量少[ ]

A．①②

B．③④

C．①③

D．①④

--How about your journey to Mount Emei?

--Everything was wonderful except that our car _________ twice on the way． 

A．slowed down

B．broke down

C．got down

D．put down