The correct answer is: should.
The word “should” is used to express a strong recommendation or advice. In this case, the speaker is recommending that the listener respect their elders. This is because elders have more life experience and knowledge than younger people, and they can offer valuable advice and guidance. Additionally, respecting elders is a sign of good character and maturity.
The other options are not as strong as “should.” The word “could” is used to express possibility or ability. In this case, the speaker is saying that the listener is able to respect their elders, but they are not necessarily required to do so. The word “would” is used to express a wish or intention. In this case, the speaker is saying that they would like the listener to respect their elders, but they are not necessarily demanding that they do so. The word “ought to” is similar to “should,” but it is slightly less forceful. In this case, the speaker is saying that the listener should respect their elders, but they are not necessarily insisting that they do so.
In conclusion, the correct answer is “should” because it expresses the strongest recommendation or advice.