同学你好，该知识点来自沪江网校《雅思语法精讲【随到随学班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学你好~
When a plane was crashed in the mountain...
① was crashed语法错误（被动语态不适用于意外事件）；② mountain 应为复数（事故常涉及山脉）。
修正：A plane crashed in the mountains（主动语态，更自然）。

the only passengers, a young woman and her baby daughters, unhurt.
① 缺谓语动词；② young 冗余。
修正：but the only passengers—a woman and her baby daughters—were unhurt（用破折号更清晰，补充动词）。

After putting children inside case...
① 缺冠词；② inside不如 in自然。
She put the children in a case（明确动作主体）。

covered them all clothes she could find out...
介词错误
修正：covered them with clothes（补充介词）。

On hearing planes passing overhead, she had a idea.
a idea 应为 an idea
修正：On hearing planes passing overhead, she had an idea（更流畅）。

The woman stamped out SOS on the snow.
stamped out多用于抽象概念（如消灭疾病）
修正：she stamped SOS in the snow（stamped直接接宾语更自然）。

This was just seen by a pilot, which sent a message...
just冗余；which指代错误
This was seen by a pilot who sent a message（正确关系代词）。

祝同学学习进步~