I'm sorry you failed your exam, but you really should have worked harder recently.

• Explanation: "Should have worked" is used to express that you did not meet an expectation or obligation in the past.

You must wear your uniform whenever you are at work. It isn't optional.

• Explanation: "Must wear" indicates a strong obligation or requirement.

Please turn your mobile off. You must not use mobiles in class, it's not allowed.

• Explanation: "Must not use" expresses a strict prohibition.

When I was at school we had to work much harder than kids do nowadays.

• Explanation: "Had to work" expresses a past obligation or necessity.

It wasn't raining so I didn't need to bring my umbrella.

• Explanation: "Didn't need to bring" shows that there was no obligation to bring the umbrella because it was not raining.

There is a ban on smoking in public places.

• Explanation: Smoking in public areas is prohibited by law.

You must carry your driving license with you at all times while driving.

• Explanation: It is a legal requirement to have your driving license with you when you drive.

You are expected to pay your taxes on time each year.

• Explanation: Timely tax payments are a legal obligation.

It is your responsibility to register your vehicle with the authorities.

• Explanation: Vehicle registration is a required responsibility for vehicle owners.

You are not allowed to park in designated no-parking zones.

• Explanation: Parking in specific areas where it is prohibited is not permitted by law