The right answer is the D: They represent the simple joys of life, which are available to anyone. The old woman is eating the ripe plums from a bag and on the street, and she is eating them (not just one, but a few) with gusto, enthusiastically ("... by / the way she gives herself / to the one half / sucked out in her hand"), which could be suggesting that she is poor and hungry, yet she finds comfort and solace in them, and that's good enough for her. No matter what others, more privileged than her, may have at their disposal: she, too, has access to this simple joy of life, a bag of juicy and tender plums, which are providing a pleasurable moment that no one can deny to her.