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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2. The baby isn't drinking orange juice.

3. My son isn't doing his homework at present.

4. I and Tom aren't walking in the street now.

5. Jim isn't riding a bike.

6. Robert isn't eating chicken

`color{orange}{~LeAiFuRuiHuiBao~}`

2. The baby isn't drinking orange juice.

- Vì "The baby" là S số ít -> Dùng "is"

3. My son isn't doing his homework at present.

- Vì "My son" là S số ít -> Dùng "is"

4. I and Tom aren't walking in the street now.

- Vì "I and Tom" là S số nhiều -> Dùng "are"

5. Jim isn't riding a bike.

- Vì "Jim" là S số ít -> Dùng "is"

6. Robert isn't eating chicken.

- Vì "Robert" là S số ít -> Dùng "is"

-> Thì HTTD:

(+) S + is/am/are + V-ing

(-) S + is/am/are + not + V-ing

(?) Is/Am/Are + S + V-ing?

-> DHNB: now, at the moment, right now, at present, Look!, Listen!, Keep silent!, ...

-> Diễn tả những hành động đang xảy ra tại thời điểm nói, 1 hành động sắp xảy ra trong tương lai gần