【单选题】

By "a well-oiled cog in the machinery" the author intends to render the idea that man is______.
A．a necessary part of the society though each individual's function is negligible.

B．working in complete harmony with the rest of the society.
C．an unimportant part in comparison with the rest of the society, though functioning smoothly.
D．a humble component of the society, especially when working smoothly.