We saw AN otter.
You use ‘an’ when the next word starts with a vowel.
For example:
With vowel - There was AN eagle.
Not a vowel - There was A bird.
C, Roses have a beautiful scent and the ones in my grandfather´s garden are especially fragrant
<h2>Answer:</h2>
Formal and Precise
<h2>Explanation:</h2>
Argumentative essays are those essays which provide a perfect solution to convince someone about an idea or opinion that is why their style of writing should be formal. The tone, the choice of words and the way those words are put together must be less personal and precise. For instance we want to provide information about an incident, we should use its exact date and time which means we should be precise.
I think you should use for example, because that second sentence is an example of the first. Hope this helps.