How does the last stanza of the excerpt suggest that the speaker is moving on from the feelings described in the first stanza

C. It explains how the speaker has learned not to spend time uselessly yearning for her dead lover.

Explanation:

In the first stanza, the speaker clearly makes peace with her condition and agrees to move on with a life deprived of happiness and joy.

But the second stanza takes a different turn. The speaker checks the tears of useless passion, meaning she holds it in, she takes control. She has a far different attitude now, talking about useless passion.

After coming to terms with her situation, she realizes how useless these tears are. No matter what she does, her lover is gone. She cannot change that. So she declares how she weaned my young soul from yearning after thine - no more yearning!

The last two verses explain the speaker's final rejection of a depressing life. She no longer wants to hasten down that tomb as she is going to die anyway (already more than mine).

"the day we found the sharks' teeth" i would say highlight the element of the plot as it sets its boundaries and centers the adventures of them being on a boat and cleaning spit of sand.