First of all we need to know that the external conflict means that the main character is fighting with external problems. Such as robot vs robot, robot vs man, etc.<span>An example of this is Romeo and Juliet. In
this play, the two title
characters fall deeply in love but are from feuding families. Their struggle to
be together is external, as it is between the two lovers and society's
pressures for them to hate one another. </span>
<span>It is in fact this struggle with their society that actually causes the
tragic deaths of both title characters.
(http://study.com/academy/lesson/what-is-external-conflict-in-literature-definition-types-examples.ht...)</span>
In an expository essay, you are only asked to describe what your task is, it should be objective and distant, with no poetic vocabulary or what not. So, the correct answer is A, formal, because the other options do not fit here.
