1. Alexandre Eiffel designed Eiffel tower for the paris world's Fair of 1889

-> Eiffel tower was designed for the paris world's Fair of 1889 by Alexandre Eiffel 

2. They performed Christmas songs for people in town

-> Christmas songs were performed for people in town

3. Santan Claus gave children presents on Christmas Eve

-> Children were given presents by Santan Claus on Christmas Eve.

*Kiến thức CBĐ QKĐ : S + was/were + P2 by O

$\text{Cấu trúc:}$ `\text{QKĐ bị động:}` $\textit{S + was/ were + V3/ed + (by O).}$ 

`1.` Eiffel tower was designed for the Paris world's Fair of 1889 by Alexander Eiffel.

`->` Eiffel tower là danh từ số ít `=>` dùng "was"

`2.` Christmas song was performed for people in town. (* Lưu ý: performed ko phải ferform nhé cậu, Christmas ko phải Chiristmas nhé!)

`->` Christmas song là danh từ số ít `=>` dùng "was"

`3.`  Cách 1:  Children were given presents by Santa Claus on Christmas Eve (Lưu ý: Santa Claus ko phải Santan Claus nhé cậu)

`->` Children là danh từ số nhiều `=>` dùng "were"

`-` Trong câu bị động, trạng từ chỉ thời gian luôn đứng sau by O.

Cách 2: Presents were given to children by Santa Claus on Christmas Eve.

`->` Presents là danh từ số nhiều `=>` dùng "were"

`-` Trong câu bị động, trạng từ chỉ thời gian luôn đứng sau by O.