例句-1:For months, motorists had been speeding down Main Avenue. They caused a number of accidents including pedestrians being hit. That's when more police officers were assigned to enforce the law. It's worked. Since we cracked down on speeding, there have been fewer problems.
例句-2:I know the employee manual says that we only have an hour for lunch. But once in a while I have an errand to run and I get back a few minutes late to the office. My new boss is so strict about the rules. She's taking notes on anyone who's not at his desk on time. She's really cracking down on us.