As formas verbais do ''modal verb'' ''have to'' são as seguintes:

1. When did Mary have  to wear a uniform?

2. She didn't have to use  her access card.

3. He'll have to help  his co-workers with the report.

4. Did they have to go to the company yesterday morning?

5.  Will Bruno and Carlton have to visit  Sarah after the ceremony?

6.The employees had to punch the clock when they arrived at work.

7. He won't have to do extra hours this month.

8.The guys didn't have to save the money for their trip.

9.We'll have to be careful about these topics.

Como usar ''have to''

É um ''modal verb'' muito usado na língua inglesa e expressa uma obrigação ou necessidade.

No ''simple present'' afirmativo:

• They have to wait for us.
• John has to go to work today.

A forma negativa de ''have to'' no simple present é:

• ''don't have to + verbo na forma base'' , no ''simple present'' - com os sujeitos ''I - we - you - they''.
  - I don't have to go home now.
  - You don't have to say anything.
  
  
• ''doesn't have to + verbo na forma base  com os sujeitos ''He - she - it''
  - She doesn't have to study today.
  - He doesn't have to work today.

No ''simple past'', deve ser ''didn't have to + verbo na forma base'' para todas as pessoas do verbo.

• I didn't have to work last Sunday.
• He didn't have to wait a long time.

Forma contraída

• have to / has to - sujeito + 've to - sujeito + 's to
  I've to wake up earlier tomorrow. (I have to...)
  She's to go to work in the morning.

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