1. I bought a new scarf to my sister for her birthday.

=> The scarf was bought by my sister for her birthday

- QKD:

( + ) S + V ( 2 / ed )

( - ) S + did + not + V - inf

( ? ) Did + S + V - inf?

- Bị động QKD:

( + ) S + was / were + V ( 3 / ed )

( - ) S + was / were + not + V ( 3 / ed )

( ? ) Was / were + S + V ( 3 / ed )?

- A new scarf => danh từ số ít => dùng " was " 

2. Venedic is visited by a lot of tourists every year

- HTD:

( + ) S + V - s / es

( - ) S + do / does + V - inf

( ? ) Do / does + S + V - inf?

- Bị động HTD:

( + ) S + tobe + V ( 3 / ed ) 

( - ) S + tobe + not + V ( 3 / ed )

( ? ) Tobe + S + V ( 3 / ed )?

- Venedic => danh từ số ít => dùng " is " 

3.  Classical music is always listened by my mother.

- Classical music => danh từ số ít => dùng " is "

@ kyu

1. A new scarf was bought to my sister for her birthday.

-> Bị động QKĐ : S + was/were + P2 (by O).

-> A new scarf là số ít, vậy dùng Was.

2. Venedic is visited by a lot of tourists every year.

-> Bị động HTĐ : S + am/is/are + P2 (by O).

-> Venedic là số ít, vậy dùng Is.

3. Classical music is always listened by my mother.

-> Bị động HTĐ : S + am/is/are + P2 (by O).

-> Classical music là số ít, vậy dùng Is.