Option C is the correct phrase that actually adds verbal irony to the paragraph.
Verbal irony is known to take place when the intention of the speaker is to speak the opposite of what he/she means. It is a figure of speech.
From the given paragraph, we discover that Jamile's summaries even included the comments made by every council member. So, instead of Dina to directly say that the summaries contain so much details and takes time to read, the use of verbal irony states the opposite; that it contains minor details.
According to the famous author, regarding the topic of flow in dialogue, one way that a text could be read without effort suggests that the text was written smoothly as the inspiration for it came naturally.