Answer
Experimentally it is seen that in Benzene, every C-C bond length is same & this bond length is greater than C=C bond length but shorter than C-C bond length. So, we can conclude that it is neither single nor a double bond. A partial double bond characteristics is present between every two Carbon atoms. This happens because of delocalization of $\pi$ electrons which is called resonance. So, not a single structure represents benzene molecule but combination of two structures i.e. a resonance hybrid which can be represented as below:
Work Step by Step
In Benzene, every C-C bond length is same & this bond length is greater than C=C bond length but shorter than C-C bond length. So, we can conclude that it is neither single nor a double bond. A partial double bond characteristics is present between every two Carbon atoms. This happens because of delocalization of $\pi$ electrons which is called resonance. So, not a single structure represents benzene molecule but combination of two structures i.e. a resonance hybrid which can be represented as below: