The plane that divides the heart into a right and left heart is called the sagittal plane (a).
The sagittal plane is an imaginary vertical plane that divides the body into left and right halves. In the case of the heart, the sagittal plane runs from front to back, separating the heart into a right and left side. This division is important because the right side of the heart receives deoxygenated blood from the body and pumps it to the lungs for oxygenation, while the left side receives oxygenated blood from the lungs and pumps it to the rest of the body.
To visualize this, imagine cutting the heart in half from front to back. The resulting halves would be the right and left sides of the heart.
Other planes mentioned in the options are not the correct answer for this particular question. The coronal plane (b) is a vertical plane that divides the body into front and back halves. The transverse plane (c) is a horizontal plane that divides the body into upper and lower halves. The midsagittal plane (d) is a specific type of sagittal plane that divides the body into equal left and right halves.
In summary, the sagittal plane (a) is the correct answer for the plane that divides the heart into a right and left heart.