The answer should be either "or a circle." OR "or the circle."
Explanation; A good rule of thumb to use when deciding to use "a, an, the" is to read the sentence out loud with each article and you can usually rule out one or more of the answer choices because the wrong ones will not sound right if you say it out loud
When you use chronological order, you arrange the events in the order that they happened. If you're following the evolution of a character you should use chronological order.
