Select the correct passive voice form of the given sentence.

The children are doing hard work.

Hard work is being done by the children.

The correct passive voice form of the given sentence "The children are doing hard work" is Hard work is being done by the children.

The active voice of the sentence is "The children are doing hard work." This sentence is in the present continuous tense, which is used to describe an action that is happening now but is not finished. The passive voice of the sentence is formed by putting the subject of the active sentence after the verb "to be" and the present participle of the main verb. In this case, the subject of the active sentence is "hard work" and the main verb is "do." The present participle of "do" is "doing." So, the passive form of the sentence is "Hard work is being done by the children."

The other options are incorrect because:

• Hard work is done by the children." This sentence is in the simple present passive voice, which is used to describe an action that happens regularly or happens now. However, the action of doing hard work is not happening regularly or now.
• Hard work had been done by the children." This sentence is in the past perfect passive voice, which is used to describe an action that happened in the past before another action happened. However, there is no other action mentioned in the sentence.
• Hard work was being done by the children." This sentence is in the past progressive passive voice, which is used to describe an action that was happening but is not finished. However, the action of doing hard work is happening now.