vertical trace的用法和样例：
例句
- But in the counties I visited, even including those that were formerly bandit-ridden, there was no trace of bandits.
至于土匪，则我所走过的各县全然绝了迹，哪怕从前是出土匪很多的地方。 - Because any trace of water would evaporate in the Sun's heat, astronomers do not believe that debris trails contain ice.
由于水在太阳辐射下会汽化，天文学家们认为这里的尾迹并不含有冰。
