.

He chose to teach in a western province, though he _______in the city for a better life.

A．could stay

B．would stay

C．could have stayed

D．had stayed

高程控制网采用三、四等水准测量，对于大型企业用三等水准作首级水准网，而用四等水准加密，小型企业用四等水准一次布设。( )