Transformation and tense
- be (correct tense) + past participle.
- has built → has been built; is building → is being built.
Style
- Passive suits formal reports and when the doer is unknown.
- Do not overuse the passive in narrative writing.
Key idea
The passive (be + past participle) must keep the original tense; it suits formal writing and unknown doers.
Remember
Perfect passive uses 'has/have been + past participle'.