The last one because it make the most sense
By talking about the farm they're going to have in the future with all the rabbits and alfalfa that Lennie can tend to. Lennie loves rabbits and can't wait to take care of them, but he never gets to.
Taking the whole poem into account, I think the correct answer must be C.
The jar is a small, common, impersonal object, but in Stevens' view, it affects the nature, depriving it of its inherent wilderness. Although it is one of a thousand, it still has the power and dominion over nature. Its meaningless existence leaves a negative trail in this world. If the jar was regarded as faceless a person living in a highly commercialized, industrialized world, and the nature as freedom, the parallel would be all the more effective.
