The present invention relates to a composition for producing naturally-degradable substitutes of plastics and to a method for producing a granular combination of naturally-degradable polymers suitably usable in the plastic transformation industry. A database contains selected information about each of the media elements. the guard ring 13 is provided with opening portions 13a at positions where the guard ring 13 coincides with adjacent two end portions of the neighboring magnets 12. The chair cause the turning pivot of the chair back and the human body on the same line by providing the articulated point of the chair back and the base at the trochanter of the human body in the pitching movement.