Which suffix is related to the study of a substance?

The suffix that relates to the study of a substance is typically “-logy,” which refers to the study or science of a particular subject or field. The answer you have indicated as correct, "-logous," does not accurately convey the meaning. The correct suffix for the study of a substance would involve "-logy," as seen in terms like "biology" (the study of life), "geology" (the study of the Earth), etc.

The other suffixes listed do not pertain to the study of a substance specifically:

• “-therapy” refers to treatment, usually in a medical context, indicating an action rather than a field of study.

• “-crit” is often associated with measurements or evaluations, such as in the term "hematocrit," but it does not imply the study of a substance.

• The suffix “-o” is typically a combining vowel used in medical terms but does not hold a meaning related to the study itself.

Thus, understanding the precise meanings of suffixes helps in determining the appropriate choice about their relation to the study of various domains, including substances.