The correct answers would be "using contractions, slang terms, and colloquial expressions" and "using expressive punctuation". This way the writer brings the topic closer to the reader by making it "sound more like conversation". If you use "formal rules of grammar", it does not sound like a conversation, and "underlining words for emphasis" only draws your attention to those words. Mentioning your friend in the letter doesn't really affect anything.
Answer:
A. would be your user xx!
Explanation:
Hi there! I feel that C.) would be the best answer for this question. Fighting in a war wouldn't show that you value the culture of your homeland, like shown in answer A.). B and D seem irrelevant to the question at hand, and since the language of a country relates directly to the culture and answer C.) shows that Juhan values it, it'd be safest to go with that answer.