Final answer:
A plane that divides an animal into equal right and left portions is called a sagittal plane.
Step-by-step explanation:
The correct answer is a) Sagittal.
A plane that divides an animal into equal right and left portions is called a sagittal plane. This plane is perpendicular to the transverse and frontal planes. It divides the body or an organ vertically into right and left sides. If this vertical plane runs directly down the middle of the body, it is called the midsagittal or median plane.