-----Is this the first time you           Quanzhou?

-----No. But the first time I           here, the city wasn’t so beautiful.

A．visited; came

B．visited; have come

C．have visited; have come

D．have visited; came

某挡土墙高5m，墙背直立、光滑、墙后填土面水平，填土重度γ=19kN/m³，φ=30°，c=10kPa，试确定：（1）主动土压力强度沿墙高的分布；（2）主动土压力的大小和作用点位置。