Understanding prefixes that describe location helps decode medical terms. Outside is conveyed by exo-; you can see it in words like exoskeleton or exterior, where the meaning is something located outside or outer. The other prefixes here point to different ideas: endo- and intra- mean inside or within, while eu- means good or true rather than position. So the prefix that means outside is exo-.

Elective surgery refers to a planned, non-emergency operation that can be scheduled in advance. It isn’t about immediate life-or-death action, and the timing can be arranged to suit the patient and surgeon, even though the procedure may be medically necessary in some cases. Examples include cataract removal or joint replacement. By contrast, urgent surgery needs to happen soon to prevent harm, and emergency surgery must be performed immediately. Muscle tone is unrelated to this concept.

Histology is the study of tissues. It focuses on the microscopic structure of tissues—the arrangement of cells into organized layers and networks, and how that structure supports function. In practice, histology uses thin tissue sections, special stains, and microscopes to reveal details not visible to the naked eye. This makes it the best fit for asking about the study of tissues. Epithelial is a type of tissue, anatomy is a broad study of body structure, and microbiology looks at microorganisms, not tissues.

Antisepsis is the use of chemical agents to prevent or inhibit the growth of pathogenic organisms on living tissue. This fits the description because the goal is to suppress microbial growth where the body is exposed, reducing infection risk. The other terms are not about antimicrobial processes: leukopenia is a low white blood cell count, affecting immune defense but not describing a growth-inhibiting procedure; cardiopulmonary relates to heart and lung function; pericarditis is inflammation of the pericardium. Antisepsis differs from disinfection (which targets inanimate surfaces) and sterilization (which aims to kill all microorganisms). In practice, antiseptics like chlorhexidine or alcohol prep skin to prevent infection.