Which body plan allows an organism to be divided into mirror-image halves along one plane?

Bilateral symmetry is the correct answer because it describes a body plan in which an organism can be divided into two mirror-image halves along a single plane, typically the sagittal plane. This organization is characteristic of many animals, including humans, where the left side and right side are reflections of each other.

In the context of body plans, bilateral symmetry allows for a more streamlined shape that can facilitate movement and is often associated with more complex behaviors and functions, such as predatory and locomotive abilities. This arrangement is advantageous for organisms that move through their environment, as it enables directional movement.

Radial symmetry, in contrast, allows an organism to be divided into similar halves along multiple planes passing through a central point, which is typical of organisms like jellyfish. Asymmetry refers to organisms that do not have a defined shape or plane of symmetry, such as sponges. The term symmetry lacks specificity and does not relate directly to how the body plan divides, making bilateral symmetry the most accurate answer within the context of the question.