Superlatives are verbs that show degree, examples are good, better, best OR bad, worst, worse.
Because there are three or more being compared you want BEST so that answer is most skillfully.
Well i can't really answer that question because there is no document shown.
The answer is B, as it helps not only to keep the reader's attention but to also inform or persuade them more to a topic. In addition, it is also sometimes used to help convey a specific emotion, thus helping the reader get more into the text.