MITIGATE :

The correct answer is: A. Abate.

To mitigate something is to make it less severe or intense. For example, you might mitigate the risk of a fire by installing smoke detectors and a fire extinguisher.

The other options are incorrect because they have different meanings.

• To aggravate something is to make it worse. For example, you might aggravate a headache by drinking caffeine.
• To allay something is to make it less worrying or frightening. For example, you might allay someone’s fears by telling them that everything is going to be okay.
• To alleviate something is to make it less painful or uncomfortable. For example, you might alleviate a headache by taking a painkiller.

I hope this helps!