In connection with the premises, (A) establishes that audiences don’t take any interest in the characters in Brecht’s plays. This implies that they won’t care about what happens to those characters, which in turn allows us to conclude that Brecht’s plays are not successful dramas.

The issue is whether audience’s difficulty in discerning the characters’ personalities implies an audience doesn’t care about the characters. What determines the characters’ personality is irrelevant.

We already have as a premise the idea that succeeding as a drama requires that the audience cares about at least some of the plays’ characters. What’s missing is that we don’t have a way of establishing that the audience does not care about any characters in Brechts’ plays. (C) doesn’t provide us with that missing piece.

We already know that the audiences of Brecht’s plays find it difficult to discern any of the characters’ personalities. What matters is the relationship between this and audiences’ caring about the characters.

(E) tells us that certain plays succeed as dramas. But we’re trying to prove that Brecht’s plays do NOT succeed as dramas.