假山内部山洞洞壁的结构形式有：（）。
参考答案：墙式洞壁、墙柱式洞壁
Yesterday I _________ to the park by bus. Now, I am ________ to the park.[ ]
A. go; walk
B. went; walked
C. went; walking
Between the two buildings _____ a monument.
A．stand
B．stands
C．standing
D．isstanding
