The correct answer is B) rivalries between classes.
The other options of the question were A) defeat in the Punic Wars. C) a refusal to build a navy. D) the invasion of Muslim armies.
What was a factor in Rome transition from a republic to an empire was "rivalries between classes."
In 509 BCE, the Roman Republic had been founded, installing a representative democracy after many years of Etruscan rule. It was after Julius Caesar's death, that his nephew Augustus became the first Roman Emperor, and the Republic became a thing of the past. Many things changed but the differences and rivalries between classes remained.