英语改错：Once to be begun,the plan will never be changed 哪里错了?

to be begun 改成 begins
（相当于：once it begins，省略it)
不需要被动语态，计划开始（不需要说“被开始”），但改变计划，计划是被改变的，所以后面是要用被动语态的

be changed 改为 changed

Once begun,the plan will never be changed
去掉 to be
once省略结构
还原为Once it is begun,the plan will never be changed
it指代the plan

可以将once begun 视为一固定表达，该句展开就是：Once it has begun, the plan will never be changed.
Once begun 是“一旦开始”的意思。又如：
Once done, we won’t regret doing so.
Once elected, he will move forward swiftly to set a new club.