Answer:
Science fiction assumes that the universe bursts with life, but scientists aren't so sure.
Explanation:
According to the given paragraph about the low probability of finding life in other planets or galaxies, the most effective topic sentence for the paragraph is Science fiction assumes that the universe bursts with life, but scientists aren't so sure.
This is because, a topic sentence is a brief statement of the main point of an essay.
A. it is missing a subject,verb,or complete thought
