Final answer:
Nodding in the body requires the action of a first-class lever.
Step-by-step explanation:
The action of a first-class lever is required in nodding in the body. A first-class lever consists of a fulcrum located between the effort and the load. In the case of nodding, the fulcrum is the joint between the skull and the first vertebra, the effort is applied by the muscles to tilt the head backward or forward, and the load is the weight of the head.
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