The correct answer is A.
In the second stanza of the poem "Love after Love" the self is compared to a stranger.
In Line 7, the poems reads: "You will love again the stranger who was your self". This suggest that the visitor is an image of his past. Him, but in a younger version, in a time in which he could still love himself. But the speaker has been through much and has change deeply, and for this, his younger version seems like a stranger.