Step 1: Fix the meaning of the given pair.
$Exacerbate$ means to make a bad situation worse, while $mitigate$ means to make it less severe or intense. The relationship is direct opposites on a worse-versus-better scale.
Step 2: Check each option word by word.
$Aggravate$ also means to make worse, matching $exacerbate$, and $alleviate$ means to reduce the severity of something, matching $mitigate$. The other three options pair a worsen word with a word that does not mean ease (precipitate means to trigger suddenly, exonerate means to clear of blame).
Step 3: Confirm there is no closer match.
No other option keeps both halves of the worsen-versus-ease relationship intact, so aggravate and alleviate is the only pair that mirrors exacerbate and mitigate.
Final Answer:
The pair that repeats the same opposite-meaning relationship is aggravate and alleviate.
\[ \boxed{\text{Aggravate : Alleviate}} \]