Which of these examples is not periodic?
Calendar
Notes on a scale
Rain
Seasons

fumikage isn't really a bird, and tsuyu does have teeth. tsuyu has a transformation quirk which still allows her to be partially human. otherwise we'd have a large frog running around. fumikage has teeth because again, he isn't a bird. his head was a quirk mixture if i'm correct.

the cover letter for a job search includes the skills one has for the particular job. including a cover letter is always a good idea, as it describes the ability to perform a task, and the employer can easily fetch the intention of the job you want to do.  

the cover letter is very important to be included in the job search document. hence, i strongly with the statement.