I chose B and E but I as very confused between A and B. How do we understand what to choose here?

Nothing to be confused.

If someone is in prison for some reason then he/she gets used to staying inside. It is like creating your own microcosm and when you are out you feel like lost and not comfortable. Several studies in the real world noticed this.

Aversion means a complete rejection of the outside world, in this case. Instead, the logic blank is that you are reluctant or you do have doubts

The best pair to complete the sentence is:
(i) reluctance about
(ii) exhortations

Explanation:
- Former prisoners-of-war often show a notable "reluctance about" rejoining the outside world, meaning they are hesitant or unwilling to leave the confinement they have become used to psychologically.
- Despite the "exhortations" (strong urges or encouragements) of their emancipators (those who freed them), the prisoners prefer to remain in their familiar prison cells, which feel less threatening due to familiarity.
- Other options do not fit the expected tone and context as well as these. For example, "aversion to" is similar but "reluctance about" is more commonly used in this kind of formal expression; "nonchalance" (indifference) and "faults" do not suit the encouragement context.

Thus, the full sentence reads:
"The psychological costs of confinement become apparent when certain case studies involving prisoners-of-war are reviewed. Often, when granted freedom, former captives display a notable reluctance about rejoining the outside world, and despite the exhortations of their emancipators, prefer to remain inside their more familiar, and thus seemingly less threatening, prison cells."