被动语态（过去式） The Passive Voice (Past Tense)
Sentences in the past tense can be said in the passive voice.
The Past Tense
He kicked the dog
The Passive Voice
The passive voice is formed by:
be (in the correct tense) + p.p.
For the past tense, that is:
was/were + p.p.
The dog was kicked
Sentences in the past tense using the passive voice
(active) I ate the apple
(passive) The apple was eaten by me
(active) A fire destroyed the library in 1922.
(passive) The library was destroyed by a fire in 1922.
1.Change these sentences into the passive voice:
(i) They cut the tree down last winter.
(ii) Newton discovered the theory of gravity.
(iii) The fall broke every bone in his arm.
2. Change these sentences out of the passive voice:
(i) The scar was left here by a snake bite.
(ii) The street was flooded by the rain.
(iii) She was raised by her grandparents in the north-west of Canada.