Chuyển sang câu bị động

1 the cleaner has cleaned the office.

==>

2 he had written three books before 1867

==>

`1.` The office has been cleaned by the cleaner.

`->` Câu bị động thì HTHT

$\text{S + have/has + P2}$

`2.` Three books had been written before `1867`.

`->` Câu bị động thì QKHT

$\text{S + had + been + P2}$

$chucbanhoctot$

$\textit{~KaitoKid!}$