1. The ruthless sea; the author’s melancholy feeling when his ideals are shattered in the complex social life.
2. Feudal ethics and conservative forces that stifle love.
3. C
4. C
5. "I" have not given up, and the "cloud-like shadow" in "my" heart is as bright as before , which makes people nostalgic. This euphemistically expresses the protagonist's deep and irreversible friendship with his lover, and his persistence in sorrow.