The correct answer is A: The rights of an individual are more important than the rights of a group.
Anthem is a dystopian novel that depicts a society in which people lack any and all individuality. This society is so against individuality that the word "I" does not even exist. At the end of the novel, the main character has fled this society, rediscovered the word "I," and rejects the ideas of his former home.
Rand clearly objects to placing the rights of the group above the rights of the individual. Answers B through D place a high value on the group, which Rand would disagree with. Only Answer A places the individual above the group, which Rand would support.
His poetic form had to be able to channel what he saw as the poetry inherent in all the infinite activities of life. It's little wonder, then, that he found it necessary to invent a poetic form—free verse—that could give him the freedom to achieve those ends.