• Modals of Deduction or Speculation

• 
• Modals of deduction are used when we are sure something is true. 
  

  -They must be rich because they live in an apartment on Fifth Avenue. 
  

  
  

  Modals of speculation: 

  We use must when we think something is true, but we are not sure.

  We use have to when we think something is true and can prove it.

  -They must know each other from before.
  

  -They have to know each other; they went to the same high school.

   

  We use can’t for negative deductions when we are sure that something is not true, or it is impossible. 

  -They can't be home because all the lights are off.
•  Click on the play button to hear the audio

• Modals of Deduction	Jack has five credit cards.  He must have a good credit score.
  Modals of Speculation	There has to be a First Bank branch close by; I see three on the map.
  Negative Deductions	You can't be broke. You just got paid yesterday!

 Source : Alison