Final answer:
The speaker's attention is concentrated on Annabel Lee chiefly because of their mutual and transcendent love, a theme central to the poem. The correct answer is because she loved the speaker.
Step-by-step explanation:
The speaker focuses his attention on Annabel Lee because she loved the speaker. Their profound love for each other is the heart of the poem, as it portrays a bond so strong that even the angels coveted it. The narrative delves into themes of love, loss, and the envious nature of heavenly beings who could not tolerate such a pure love in the earthly realm. While the poem does suggest that Annabel Lee was a young and innocent child who lived by the sea, the crucial element that captures the speaker's undying attention and adoration is the love she bore for him---a love which he believes extends beyond the grave.