Given sentence is in Past simple tense and it is in active voice, we need to change it into passive voice.
Rule : Subject + (was / were) + V3 + Optional Agents
This is an imperative sentence; passive voice of "Help him" is formed using "Let + object + be + past participle".
So, "Help him" becomes "Let him be helped." in passive voice.
This is a sentence of Present Indefinite Tense.
The formula of Passive Voice for Present Indefinite Tense to Passive Voice: Object + is/are/am + III form of verb + by+ subject.
Rule : Subject + (was / were) + V3 + Optional Agents.
Correct Passive Voice Conversion:
The original sentence ("Have you finished your job?") is in the active voice (Present Perfect Tense).
Its passive form follows the structure: "Has/Have + subject + been + past participle + by + agent?"
Thus, it becomes: "Has your job been finished by you?"
The sentence "They are painting the building" is in present continuous tense.
The correct passive form of present continuous is: is/are being + past participle, so: is being painted.
Tense: Present simple (They buy)
Passive structure: Object + is/are + past participle + by + subject
"Flowers" is plural → use "are"
Past participle of buy is bought
Correct passive voice:
Beautiful flowers are bought by them.
Nobody has touched this box.
Passive voice: This box has never been touched by anybody.
"Nobody" becomes "by anybody" in passive.
Present perfect tense is maintained: has been touched.
This is a passive voice transformation of a sentence with causative structure.
Subject "They" becomes agent in passive form: "We were expected by them to build the road."