In Lewis Carroll's "The Walrus and the Carpenter," the young oysters can be interpreted in several ways. The most fitting interpretation among the options you provided is the naive and trusting nature of the common people.
In the poem, the young oysters are portrayed as innocent and unsuspecting creatures who are easily led by the Walrus and the Carpenter. This reflects how the common people can sometimes be naive and unsuspecting of the exploitation or manipulation that may come from those in positions of power, such as the Walrus and the Carpenter, who ultimately have their own interests at heart.
While other interpretations, like the struggle against exploitation or the influence of the upper class, do have relevance, the imagery and tone suggest a more direct allusion to the innocence and trusting nature of those who may not fully understand the consequences of their actions or who may be too easily swayed by charismatic figures.