The correct answer is option a. "the transience of life".
Explanation:
The poem “When I Have Fears” by John Keats explores the meaning of death, the fear that the author has about it and what prevents him to doing it. The poem deals with the transience of life since the beginning by stating "When I have fears that I may cease to be", and until the last line by stating "Till Love and Fame to nothingness do sink". The poet wonders what will happen when his time has over and what things he would let unsolved.
