Final answer:
The medial-lateral axis corresponds to the frontal (or coronal) plane, which divides the body into anterior and posterior portions; hence, the correct answer is a) Frontal.
Step-by-step explanation:
The medial-lateral axis pertains to movements that occur in a specific anatomical plane. Specifically, this axis corresponds to the frontal plane, also known as the coronal plane. Movements around the medial-lateral axis are typically side-to-side movements that divide the body into anterior (front) and posterior (rear) portions, like abduction and adduction of limbs. Therefore, the correct answer is a) Frontal.
The other planes of the body defined include the midsagittal plane which divides the body into equal right and left halves, the transverse plane which divides the body into upper and lower portions, and the sagittal plane which can be either a midsagittal plane if it splits the body into equal halves, or a parasagittal plane if it splits the body unequally.