• Modals of Conclusion

• 
• Use a modal of conclusion when you are mostly sure about something.

  
  

  Use must or must not when you think something is probably true, but you are not a 100% certain.

  -Sara wasn't at school today. She must be sick.

  (We think Sara is sick, but we are not sure.)

  -John isn't coming to the party. He must not have time.

  (We think John doesn't have time, but we are not sure.)
• Use have to when something is probably true and you have evidence.

  -Amy eats a lot of vegetables. She has to be healthy.

  (We think Amy is healthy because she eats vegetables, but we are not sure.)
• You can also use have got to (or the contraction) for conclusions.

  -She has got to be healthy.
•  Click on the play button to hear the audio

• Alex is from the UK. He must know the Queen!	Emily didn't return my call. She must not like me.
  You are good at math. You have to be really smart!	Scott likes sports. He's got to have a favorite team.

 Source : Alison