_____ will greatly decide their future, most senior 3 students think, is their grades．

By the time he realizes he _____ a mistake, it’ ll be too late for him to change his mind. [ ]

_____the time I got to the bus stop, the bus had already left.

Jim was walking along the river_______ he heardsomeone_______ "Help! Help!

You can watch TV ______, but you can’t watch it ______ a long time.