`81` Because Lan was sick , she didn't go to school yesterday 

`-` Because + clause 1 , clause 2 

`-` Because of + N/Noun Phrase/V-ing , clause

`-` Lí do/Nguyên nhân của 1 sự việc 

`82` The tomorrow homework has just been finished by my children 

`-` Bị động thì HTHT : S + has/have + been + Vpp + ( by O ) 

`83` I used to go swimming with my brother last year

`-` used to + V-inf : đã từng làm gì

`-` Thói quen trong quá khứ nhưng nay không còn xảy ra nữa

`84` Lan finds carving eggshells so boring and difficult

`-` think sth/doing sth + is + adj

`-` find sth/doing sth + adj 

`85` When I was 6 years old, I could read an English book 

`-` Sự việc đã xảy ra và đã kết thúc trong quá khứ

`-` When + S + was/were + ... , S + Ved/V2 + O 

`1`. Because Lan was sick, he didn't go to school yesterday.

`⇒` Cấu trúc: Because + S + to be + adj, S + V

`2`. The tomorrow homework has just been finished by my children.

`⇒` Cấu trúc: S + have/has + been + Vpp + by O

`3`. I used to go swimming with my brother last year.

`⇒` Cấu trúc: used to + Vo

`4`. Lan finds carving eggshells boring and difficult.

`⇒` Cấu trúc: S + find + Ving + adj

`5`. When I was 6, I could read an English book.

`⇒` Cụm at the age of 6 = I was 6

`⇒` Cấu trúc: When + QKĐ, QKĐ