The midline that's the body is called

The body's mid-line is an imaginary line down the centre of the body that divides the body into left and right. Crossing the body's mid-line is the ability to reach across the middle of the body with the arms and legs.

b. lithosphere, asthenosphere, mesosphere   is the answer most likely

organ system-an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.