We ____ here two hours ago . We ____ here for two hours .        [ ]

A. have arrived, have been      

B. have come, have been

C. came, have come            

D. arrived, have been

下列数据中，比较符合实际情况的是（　　）

A．一支铅笔的长度约为70cm

B．教室天花板到地面的距离约为3m

C．一个鸡蛋所受的重力约为500N

D．一件普通衬衫的质量约为2g