Even though he took his son on a thorough trial run of the route two days ago, he is still worried. He estimated his son's return time and has come to the subway exit to wait for him.
縱使前兩天他已經帶著兒子仔細的試坐過這條路線，他還是不放心，特別算準兒子回程的時間，到地下鐵出口守候。