Which characteristic of government describes athens, not sparta?

a. two kings led during wartime.
b. only about 8 percent were citizens.
c. most power rested with the council.
d. all citizens could debate any issue.

The main thing that separate Athens and Sparta is Democracy.

So, the answer is D.

In Athens, all citizens are allowed to speak their mind. Athens was considered the first civilization who implement Democracy in the history. 
( Back then , citizens of Athens could voted directly on legislation and executive Bills)