轧制压力是（）作用力在垂直方向的投影。

A．金属对轧辊

B．轧辊对金属

C．金属对辊道

D．辊道对金属

He tried many times to sneak across the border to a neighboring country,（）caught each time.

A. having been

B. only to be

C. always being

D. unfortunately