A person commits drug-induced homicide by unlawfully delivering a controlled substance which causes a person's death by _____, _____, _____, or _____.

The correct answer encompasses all methods by which a controlled substance can lead to drug-induced homicide: ingestion, absorption, inhalation, and injection. This broad definition is important as it acknowledges the various ways drugs can enter a person's system and ultimately result in fatal consequences.

Ingestion refers to taking substances orally, while absorption may involve substances that enter the bloodstream through the skin or mucous membranes. Inhalation covers the process of breathing in substances, and injection involves directly introducing the substance into the bloodstream using a syringe. Each of these methods highlights the potential for lethal effects when a controlled substance is unlawfully delivered and misused, which is critical for understanding the serious consequences of drug-related offenses under Illinois law.

This comprehensive approach in the answer underscores the law's focus on the totality of situations that can arise from the unlawful distribution of controlled substances, addressing the varying ways individuals might come into fatal contact with these substances.