问题补充：
改写句子Every means has been tried,yet this machine won work.Every means has been tried,yet this machine won work.句子可以写成：-Every means tried,yet this machine won work为什么可以省略has been
答案：
学了非谓语吗?这个是独立主格结构
MEANS 和 TRY 是被动关系,所以用TRIED
且独立主格是短语形式的~
======以下答案可供参考======
供参考答案1:
Every means has been tried, yet this machine won work.
他想尽了各种办法，但是这台机器就是无法运行。
Every means has been tried 是个从句.是个完整的句子
Every means tried 只是个短语,在句子中作方式状语,所以可以省略be动词
