Food safety is one of the problems now all over the world.
It's a rule for all the students to _____ their places ahead of 5 minutes waiting for the class to be started.
On his way home, he found a wallet ____ on the ground, which he picked up and ____ in his schoolbag.
Could it be in the restaurant in ____ you had dinner with me yesterday ____you left behind your keys and wallet?
There is no need _______ and it’s no use __________ there too early.
The air is deadly polluted because some factories don’t __the rules to protect the environment.