The main thing that this question is asking is which sentence does not have a formal tone. A formal tone for research writing usually means using more professional (instead of casual, everyday) language and free of your own opinions.
This means choice D is inappropriate because it is opinionated. Using "I think" is not formal tone.
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Answer: D) I think one of the most frustrating things about owning a cat is that they don't obey many commands.
16 year olds can be immature and not follow the laws. Also they are not considered an adult until 18 so their parents would have to take care of most car stuff for them if they get in an accident
I think the best sentence in my opinion is:
"We regret to inform you that you have not been selected to interview for this position."
