围绕本课标题 By air 乘飞机（飞机折返）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：I used to travel by air a great deal / My parents used to live in South America / A flight attendant would take charge of me / I am used to travelling by air / only on one occasion have I ever felt frightened / After taking off / flying low over the city / slowly gaining height / the plane suddenly turned round / flew back to the airport / waiting to land / keep calm / as soon as it had touched down / Everybody on board was worried / curious to find out what had happened / a very important person on board / a bomb had been planted on the plane / the plane was searched thoroughly / nothing was found / we were able to take off again