分析一下新概念英语1They have been told that rescue operations are pro

分析一下新概念英语
1They have been told that rescue operations are progressing smoothly.为什么不用They was told....
2However,rescue operations are proving difficult.proving在这里是动名词作表语吗？
3If explosive are used ,vibrations will cause the roof of the mine to collapse.to collapse是什么成份？
4If they knew how difficult it was to drill though the hard rock ,to drill是什么成分？
5has enabled the men to keep in touch with their closest relatives keep前面为什么加to