Answer:
a) Confident
c) Polite
d) Serious
f) Unemotional
Explanation:
When writing a formal letter or e-mail one should bear in mind certain aspects. The general tone of your letter or email should be confident, polite, serious and unemotional. In other words, you shouldn't sound neither hesitant nor too confident, always showing that you are polite and not demanding or aggresive. Dramatic issues must not be part of your letter, and try not to involve emotions because formal letters should be objective.
As regards language, bear in mind that contractions (don't, she's, haven't) are not advisable, it is better if you use full forms. Moreover, don't use phrasal verbs and idioms.
