* In an active sentence, the subject is doing the action.
* The target of the action gets promoted to the subject position.
* Used when the emphasis more on the object of a sentence
rather than doer. If it is imperative that the doer (subject) be
mentioned, the passive sentence will include a 'by' phrase.
> People (subject) spoke (verb) Japanese (object) in Japan
> Japanese language (subject) was spoken (verb) by
people (object) in Japan. (passive sentence)
When Active change to Passive sentence, verb must change
to past participle. Past Participle cannot stand by its own. So, it
must use be verb & auxilary verb.