问题描述：
一道SAT语法题,谢谢啦!
In Germany,foresters discovered that trees killed by acid rian had begun to die four years (earlier without any signs of disease shown then.)
请问括号里的为什么错了?
In Germany,foresters discovered that trees killed by acid rian had begun to die four years (earlier without any signs of disease shown then.)
请问括号里的为什么错了?
问题解答：
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