Refer to the figures, (A, B and C) and arrange them in an order of list class lever, second class lever and third class lever.

Options

A. B,A,C
B. C,A,B
C. C,B,A
D. A,C,B

Answer

A

Explanation

Movement takes place along the joints which act as fulcurm of the level. One can observe functioning of all the three types of levers in the human skeleton.
The example of first class lever is exhibited by the joint between atlas vertebra and occipital bone of skull (figure B). When the head is raised, the joint is the fulcrum, contraction of back muscle is the effort, and facial portion of the skull acts as resistance. The second class level is exhibited by human body raised on toes (figure A). In this example, the ball of the foot is the fulcrum, the contraction of the calf muscles to pull the heel upward is the effort, and the body is the resistance. The flexing movements of the elbow of fore arm are based on the principle of third class lever (figure C). In this case, elbow joint is the fulcrum, the contraction of the biceps muscle is the effort and weight of the forearm is the resistance.