tricky question because it is fairly short but at the same time it is not dead difficult

Just read the sentence, pause a bit and reflect.

The danger of (i) ________ assumptions regarding the character of those belonging to certain social classes

If you read the sentence this way you have two options
1) the danger of something positive
2) the danger of something negative

Now, the danger of assuming X of certain social classes, inevitable, leads me to think that X is indeed the consequence of some other action that works in a way that misleads us.

In other words, we assume that the behavior of those who pertain to a certain social class is X because on the other hand, and in a persistent way, someone else depicted those members in a bad fashion.

Hulk is basically rude and unpleasant. Brute. We know him because is always depicted in this manner. This is NOT always true.

The same scenario is here

rearranging the question the other way around: because Jane Austen, in her novels, depicts the rich as always evil or similar lead us to assume all the time unfounded thinking or things or thought that NOT always are true.

We are misled by jane Austen to think always X but this is not true. Could be also Y

Hope this helps