Allusion is a figure of speech, in which an object or circumstance from unrelated context is referenced covertly or indirectly. It is left to the audience to make the direct connection; where the connection is directly and explicitly stated by the author, it is instead usually termed a reference
The "great packing machine" refers to the slaughter industry the author describes through the book. He is trying to portrait and denounce the unhealthy, dangerous, almost-enslavement condition the workers suffer in that industry.
I would say that the qualities that are generally true of both traditional and modern plays is that they contain elements such as dialogue, setting, characters, and plot.
The other options are incorrect because:
They aren't necessarily just dramas or tragedies, they could also be comedies.
The order of these events isn't that strict.
They don't necessarily resolve the conflict.
Negative connotation is when it sounds really bad like