|No choice – you have to do this
||Must / have to
||As citizens we must obey the laws of the country in which we live.
|No choice – you cannot do this
||Must not /not be allowed to / cannot
||Citizens must not break the laws of the society in which they live.
|Recommended – you should do this
||Should / Ought to
||Students choosing to study post-graduate programmes should fund their own education costs.
|Recommended – you should not do this
||Should not / Ought not to
||Children should not argue with adults.
|You can choose to do this if you want to
||To be allowed to/can/
||Many children are allowed to watch television whenever they want to.
|You can choose not to do this if you want to
||Need not / do not need to / do not have to
||In Britain, motorists do not need to carry their driving licence with them when driving their cars, which is quite unusual.
|Needs and necessities
||We need to find a solution to problems of poverty in the developing world.