The examples
Tense | Subject | Verbs | (prepositional) Object | |
Present Continuous | Active: | Rita | is writing | a letter |
Passive: | A letter | is being written | by Rita | |
Past Continuous | Active: | Rita | was writing | a letter |
Passive: | A letter | was being written | by Rita | |
Past Perfect | Active: | Rita | had written | a letter |
Passive: | A letter | had been written | by Rita | |
Future Perfect | Active: | Rita | will have written | a letter |
Passive: | A letter | will have been written | by Rita |