Which theme is most likely to be inferred from a story that is focused on an external conflict?

It seems that you have forgotten to include the choices for this question which are: A. Humans are vulnerable to the forces of nature.

b. Low self-confidence is an obstacle to success.

c. Personal flaws often have a root in childhood.

d. Greed can defeat a person like no other vice.

Therefore, the theme that is most likely to be inferred from a story that is focused on an external conflict is option A. Humans are vulnerable to the forces of nature. This is the only option that describes about external conflict. The rest is all about internal conflict.