Which of the following is non-benzenoid?
What do you mean by non-benzenoid?
Yes, as the name suggests, the compounds not having benzene ring are known as non-benzenoid compounds.
[∗ Note: - Benzene ring is not considered as a substituent ]
Now, let's consider all the options.
In option (a), (b) and (c), there is no benzene ring; therefore all the three options are non-benzenoid structure.