A serious play with an unhappy ending is classified as a tragedy. Option B is correct.
Tragedy is a form of drama based on human suffering. It generated catarsis or pleasure in the audience.
It is a serious play or drama which usually addresses the problems of a main character. Tragedy is characterized by an unhappy or disastrous ending brought on, as in ancient drama, by fate and a tragic flaw in this character.
Love and immortality because Shakespeare is saying that the love he has for his partner will live on within this poem, so she, in turn, will be immortal.