Important and insignificant are opposite. Insignificant means not important, so the correct answer would be B, peaceful.
Important is to insignificant as restless is to peaceful.
Alliteration is the figurative language for those types of sentences
A good topic sentence is very clear, focused on the topic, directly relates the thesis, summarizes the main points of that paragraph, and strongly supports a claim.
Let's say that a clock is broken, so stuck on the time 6:15. While most of the day, that clock is incorrect, it is correct at 6:15 AM and 6:15 PM, thus it is right twice a day.
