We were swimming in the lake _____ suddenly the storm started.

Parents and teachers should help teenagers control their use of computer games ______be controlled by themselves.

     the instructions on the packet when you take the drug and it, I think ,will work soon.

—Did you receive the letter the next day?—No. Somehow, it was three weeks ________ I received it.

—Don't you think Jim was brave to go bungee jumping?—Personally，I thought he was ________ brave.