What three elements are present in every chemical classified as an "alcohol"?

The correct choice identifies the essential elements that define the chemical structure of alcohols. Alcohols are organic compounds characterized by the presence of a hydroxyl group (-OH) attached to a carbon atom. In order to form the structure of alcohols, they necessarily contain hydrogen and carbon, which are fundamental components of organic molecules. Additionally, oxygen is present due to the hydroxyl group.

The combination of hydrogen, carbon, and oxygen is crucial because it allows for the formation of various alcohols, each differing in the number of carbon atoms, which contributes to their unique properties and behaviors. This relationship among the three elements is foundational in organic chemistry, particularly in the study of alcohols and their functionalities.

In contrast, the other combinations of elements listed do not adequately represent the structure of alcohols. Nitrogen, while an important element in many organic compounds, does not belong to the alcohol classification; helium is a noble gas and not typically a part of organic molecules; and nitrogen does not participate in the common structure of alcohols. Thus, hydrogen, carbon, and oxygen are essential and correctly identify the elements found in every chemical classified as an alcohol.