The correct option is A a description of decay
The phrase 'Blear eyes fallen from blue' imply that the woman's bright blue eyes are now dim of perception. The poet then goes on to say that this woman's perfections are now all tarnished but it was not a long time ago that she was a great beauty. This must mean that the dimness of her eyes (and her tarnished beauty) is most probably due to decay that is associated with old age or death. However, the use of "yet it is not long since" removes from consideration the slow decaying of old-age. In this context, we can say that the last stanza most prominently gives away a description of decay. Here, option A best befits the context.