围绕本课标题 SOS 呼救信号（雪地求生）主题，AI 老师会出 若干个简单问题，
每个问题听完后，用 完整句子口头作答。
⚠️ 尽量说完整句子，不要只说一个词；优先用本课句型与词语：a light passenger plane flew off course / it crashed in the mountains / its pilot was killed / The only passengers / a young woman and her two baby daughters / were unhurt / Snow lay thick on the ground / the nearest village was miles away / she turned a suitcase into a bed / covering them with all the clothes / it got terribly cold / as near as she could to the children / she heard planes passing overhead / how she could send a signal / she had an idea / She stamped out the letters SOS in the snow / sent a message by radio / It was not long before a helicopter arrived on the scene / rescue the survivors