What is the resonance structure for #C_6H_6#?
The following diagram represents the resonance structures of benzene,
The circle inside the benzene ring on the right indicates that all C-C bonds are equal.
The following diagram shows a different way that a benzene ring is represented that you may see in your studies. The carbon atoms at the six points are not drawn, but are understood to be there.
Sometimes the hydrogens are left off, too. The following diagram shows the resonance structures of benzene with the location of the carbons identified by number. This makes it easier to see how the two resonance structures are different. You can't just flip them around and make them the same.
The following diagram shows how to represent the resonance structures of benzene without the carbons, hydrogens, or numbers, which you may see in your studies.