Công thức thì HTTD 

(+) S + am/is/are + Ving 

(-) S + am/is/are + not + Ving 

(?) Am/Is/Are +S +Ving? 

I + am

S số ít, he, she, it + is

S số nhiều, you ,we, they + are

DHNB: now, right now, (!), at present, at the moment,.....

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11. aren't cooking 

12. am not watching 

13. Is / cooking 

14. Are / walking 

15. Are/ writing 

16. Is / driving 

17. are / doing 

18. is / going 

19. are / crying 

20. is / reading

`color{orange}{~MiaMB~}`

`11.` aren't cooking

`12.` am not watching

`13.` Is she cooking

`14.` Are they walking

`15.` Are you writing

`16.` Is your brother driving

`17.` are you doing

`18.` is she going

`19.` are they crying

`20.` is he reading

`__________________________`

`***` HTTD:

`(+)` S + am/is/are +  V_ing + O
`(-)` S + am/is/are + not + V_ing + O

`(?)` Am/is/are + S +  V_ing  + O?