Question

which of the following was NOT a threat to the stability of the weimar republic

Answer 1

This one is a bit tricky. I'd lean towards D. German industrialists.

Although Germany's economy was in the gutter, there were still enough wealthy and powerful people in the country to want to see it succeed. It was some of these sane industrialists that helped back Hitler's campaign in the 30's to become Chancellor.

As for the others:

A) There were a number of groups very early on in the 20s that were conservative supporters of the old system and believed that the current government had stabbed the military in the back during WW1. Uprisings led by these groups were not uncommon.

B) Communists were particularly dangerous in the early years of the Weimar republic and had also led their own uprising before it was put down, but they continued to be agitators that continued to incite anger and violence.

C) The brutal reparations imposed on Germany by the Treaty of Versailles were at the root of many of these problems, not the least of which was contributing to the wreckage of the German economy. It was a brutal condition that many believed the government should never have agreed to and only aided in Germany's humiliation as well as breed a lot of internal hate and frustration.