A(n) refers to a substance or treatment that is often used in an experiment but does not have an actual medicinal or experimental benefit. a. extraneous variable b. placebo c. confounding variable d. independent control  

A(n) B. Placebo refers to a substance or treatment that is often used in an experiment but does not have an actual medicinal or experimental benefit.

The "Placebo" is a type of "Medicine" that does not actually contain medicine, and is used to trick the users mind into solving the problem they have.

answer and explanation;

composition refers to both the types of minerals within a rock and the overall chemical makeup of the rock while texture refers to the size and arrangement of the minerals or grains that make up a rock. both composition and texture can be used to classify rocks, such as igneous rocks. texture describes how the rock became solid or crystallized from liquid, melted rock. composition of a rock describes the minerals that make up a particular rock.