I used to travel by air a great deal when I was a boy. My parents used to live in South America and I used to fly there from Europe in the holidays. An airhostess would take charge of me and I never had an unpleasant experience. I am used to traveling by air and only on one occasion have I ever felt frightened. After taking off, we were flying low over the city and slowly gaining height, when the plane suddenly turned round and flew back to the airport. While we were waiting to land, an airhostess told us to keep calm and to get off the plane quietly as soon as it had touched down. Everybody on board was worried and we were curious to find out what had happened. Later we learned that there was a very important person on board. The police had been told that a bomb had been planted on the plane. After we had landed, the plane was searched thoroughly(被彻底搜查). Fortunately, nothing was found and five hours later we were able to take off again.
根据短文内容判断正（T）误（F）

人体的肩关节、髋关节、肘关节和膝关节都仅能在一个平面上转动。

已知$\tan \theta =2$，则${\sin }^2\theta +\sin \theta \cos \theta -2{\cos }^2\theta =$（  ）