I'd say probably when the person you are contacting prefers communicating via call or text or another form of messaging. For almost anything professional or business related, it would be appropriate and acceptable to email.
<span> The comment on a peer’s research essay that clearly addresses problems with supporting evidence is D. The reason you discuss in paragraph 2 does not seem to fit with you claim. This comment is very important for giving correct reason that would fit with a claim has direct impact to the research paper. Therefore, this problem should be properly address to make the research valuable.</span>