If you want to inform your customers about a new service but also about policy changes or price changes and similar things, you use memos. This is the best option from these four. Because memo is a brief, straight to the point and informal way of communication that is usually used with the customers.
I would definitely go with B because a subjunctive is an realist mood (one that does not refer directly to what is necessarily real) – it is often contrasted with the indicative, which is a realist mood. Subjunctives occur most often, although not exclusively, in subordinate clauses, particularly that-clauses.
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Ethos is a mode of persuasion used to convince the audience. It is one of three artistic proofs (ethos, pathos, and logos).
Ethos is also known as ethical appeal and convinces your audience of credibility and character. It is used to prove you are worth listening to. Ethos can be developed by choosing language that is appropriate for the audience and topic (this also means choosing the proper level of vocabulary), making yourself sound fair or unbiased, introducing your expertise, accomplishments or pedigree, and by using correct grammar and syntax.
