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）

（ $1$ ）将天平放在水平桌面上并调节天平平衡．

（ $2$ ）用天平测出____的质量，记为 $m_0$ ．

（ $3$ ）在瓶中装满水，拧紧瓶盖，____，记为 $m_1$ ．

（ $4$ ）____，记为 $m_2$ ．

（ $5$ ）则牛奶的密度 $\rho =$ ____（写出表达式，用测量量的字母表示，水的密度用 ${\rho }_{水}$ 表示）．