Select the option that expresses the given sentence in passive voice.

She is holding free classes for the poor.

Free classes are being held for the poor by her.

The correct passive voice form of the given sentence is Free classes are being held for the poor by her.

The active voice of the sentence is "She is holding free classes for the poor." This sentence is in the present progressive 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 "she" and the main verb is "hold." The past participle of "hold" is "held." So, the passive form of the sentence is "Free classes are being held for the poor by her."

The other options are incorrect because:

• Free classes are being held by the poor for her. This sentence is in the passive voice, but the subject of the sentence is "the poor." This is incorrect because the poor are not the ones holding the classes.
• The poor are holding free classes for her. This sentence is in the active voice, not the passive voice. The passive voice is formed by putting the subject of the active sentence after the verb "to be" and the past participle of the main verb. In this case, the subject of the sentence is "the poor," and the main verb is "hold." The past participle of "hold" is "held." So, the passive form of the sentence would be "Free classes are being held for her by the poor."
• Free classes have been held for the poor by her. This sentence is in the present perfect tense, which is used to describe an action that has happened in the past and is still relevant to the present. However, the action of holding free classes for the poor is not happening now.