`20`.was built

`\rightarrow` Câu bị động - Thì QKĐ : `\text{S + was / were + V3 / PII ( by O )}`

`21`.arranging / helps

`\rightarrow` Cấu trúc : S + find + V-ing / N + adj

`\rightarrow` Thì HTĐ : S + V s / es / không s , es

`22`.Have you ever met ?

`\rightarrow` Thì HTHT ( CNV ) : Have / Has + S + V3 / PII ?

`\rightarrow` Đặc điểm nhận dạng : ever

`23`.donated

`\rightarrow` Thì QKĐ : S + Ved / V2

`\rightarrow` Đặc điểm nhận dạng : last

`\text{@ Fox}`

`20.` was built

`\text{→QKĐ bị động: S + was/were + Ved/VPII + (by + O) + ...}`

$\textit{→nhận bik: in 1706}$

`21.` arranging `-` helps

`\text{→find sth/doing sth + adj}`

`\text{→HTĐ: S + V(s/es) + ...}`

`22.` Have you ever met

`\text{→HTHT: Have/Has + S + (ever) + VPII + ...?}`

`23.` donated

`\text{→QKĐ: S + Ved/VPI + ...}`

$\textit{→nhận bik: last week}$