D. Josie will lead the discussion it is about a topic she knows well.
Explanation:
A fused sentence also exemplifies a run-on sentence that lacks a proper conjunction or punctuation mark(comma or semicolon) where the two independent clauses run together. These sentences are generally treated as errors that can be rectified by adding an appropriate punctuation mark or a subordinate or coordinate conjunction.
Thus, the sentence that exemplifies this claim would be the last option "Josie will lead the discussion it is about a topic she knows well" which would read as following after fixing this error:
<em>"Josie will lead the discussion </em><u><em>as</em></u><em> it is about a topic </em><u><em>that</em></u><em> she knows well".</em>
