This story hills like elephants is mainly about a a. misunderstanding b. bar c. country d. decision

The best answer here is D, a decision. The entirety of the story centers around the choice that the American and his girlfriend must make. The story itself is rather vague, never coming out and saying what it is they're making said decision about, just that there is an operation that needs to take place. The entire story centers around this operation and the struggle the American and "Jig" have in making the choice to have said operation.

The entirety of this short story also takes place in a train station, which furthers the idea of their making a decision. They are in a transient place where they will board a train that will take them one way or the other, much like the decision that they must make will take them one way or the other.