passive voice

THE PASSIVE VOICE

How the passive is formed:

SUBJECT	FORM OF TO BE + 3rdFORM	ADVERB, ...
The room	is cleaned	every day.
They	are sold	as pets.
A lot of guests	are invited	to a party.

Put an active sentence into a passive one:

	Subject	Verb	Object
Active:	Bats	eat	insects.
Passive:	Insects	are eaten	by	bats.
	Subject	Verb	by	Agent

	Subject	Verb	Object
Active:	Tom	saw	the burglars
Passive:	The burglars	were seen	by	Tom
	Subject	Verb	by	Agent

Subject of the active sentence → Agent of the passive sentence

Object of the active sentence → Subject of the passive sentence

Tenses:

Tense	Active	Passive (form of to be + 3rdform)
Present tense	invite / see	am / is / are invited / seen
Past tense	invited / saw	was / were invited / seen
Future tense	will invite / see	will be invited / seen
Present perfect tense	have / has invited / seen	have / has been invited / seen
Past perfect tense	had invited / seen	had been invited / seen

http://www.english-4u.de/passive.html