Answer:
B. He is feeling nostalgic.
A. Create an unbreakable barrier.
Step-by-step explanation:
1. The stanza where we can see why the author cries is the last one:
"My eyes grow dim, and I could no more gaze;
A wave of longing through my body swept,
And, hungry for the old, familiar ways
I turned aside and bowed my head and wept."
In these lines, we learn that the author is sad because he thinks about his home country. He misses the "old, familiar ways." This means that the author cries because he is feeling nostalgic.
2. In this poem, Frost uses the image of the wall in order to symbolize the separation between people, and in particular, between neighbours. When he uses the phrase "set the wall between us," Frost implies that there is an unbreakable barrier between the two of them.