I would belive A is your answer sorry if that is wrong
B. The observers up front were asked to sit down so that the ones in the back could see. When you are talking about people, you use sit, not set.
Assuming this question is asking for a definition/synonym/"other word" for chivalrous, the answer is courteous. leaving a more comfortable seat for an elderly person is a respectful and polite gesture, which shows courtesy.
A repeated sequence of meter composed of two or more stressed and unstressed beat is called a poetic foot. if the beat is only an unstressed and stressed following each other in sequence, that is called an iambic foot.
