The best summary of the central theme, or message, of the poem would depend on the specific content and tone of the poem itself. However, if the poem reflects a sense of longing or acceptance regarding the fleeting nature of life, option B seems to capture that sentiment effectively:
B. Life is transitory and fleeting, though we wish it were otherwise.
This summary acknowledges the transitory nature of life while also implying a desire for permanence, which is a common theme in poetry about the human experience.