Answer:
D. Unhealthy working conditions.
Step-by-step explanation:
The industrial revolution brought forth several undesirable consequences, one of them, perhaps the most important one was the poor, unhealthy, and unjust working conditions that laborers had to face. This, in fact, is one of the main reasons behind most social and labor demands of the 19th century (the rise of socialism, labor unions, strikes, etc.), and they are, still today, some of the most important struggles that workers are still dealing with.