You can only be sure of_________ you have at present; you cannot be sure of something _____ you might get in the future.
The children themselves were calm enough. _________ the parents that got into a panic(惊慌).
The clever boy made a hole in the wall, _______ he could see _____ was going on inside house.
------How do you like the book? -----It’s quite different from ___ I read last month.
Can you lend me the novel ______ the other day?
I have seen trees, _____ open at sunrise and close at sunset.