The primary use of emetics is to:

Emetics are substances that are specifically used to induce vomiting. This is often done in medical situations where a person has ingested a toxic substance and immediate expulsion is necessary to prevent further absorption of the poison into the bloodstream. By triggering the vomiting reflex, emetics help to clear harmful substances from the stomach.

The other options represent different functions that are not related to the use of emetics. For instance, facilitating digestion involves processes that help break down food, which is not a role of emetics. Reducing stomach acid pertains to medications that minimize acidity to treat conditions such as heartburn or ulcers, rather than inducing vomiting. Alleviating inflammation refers to the action of anti-inflammatory drugs, which are used to reduce swelling and pain, again unrelated to the vomiting process. Thus, the primary use of emetics centers solely on the induction of vomiting, making that the correct choice.