Answer:
d) Their occupation demanded more training and skill
Step-by-step explanation:
In the early 20th century around 1914, workers in USSR, that covers modern-day Russia and neighboring countries were divided based on their skills. These divisions were made apparent through their dress codes and manners. However, the Metalworkers considered themselves aristocrats among other workers simply because "their occupation demanded more training and skill."
Note that aristocrats by definition mean a form of social class that is seen as the highest in that society. Hence, Metalworkers then considered themselves as the upper class among other workers because "their occupation demanded more training and skill."