Final answer:
Ethnic and nationalist tensions were the main force tearing apart the Ottoman Empire in the 1800s, as various national groups sought independence and the Empire confronted growing European influence and internal challenges. Option B is correct.
Step-by-step explanation:
The force that began to tear apart the Ottoman Empire in the 1800s was B. Ethnic and nationalist tensions. Starting in the 1800s, the Empire faced significant challenges from nationalism, which spurred revolts and loss of territory as various ethnic groups within the Empire sought independence. The decline of the Empire was compounded by a mix of factors, including financial troubles, increasing debt, military defeats, and internal factional politics.
Additionally, European nations began to rise as individual nation-states with a strong sense of nationalism, which drove them to compete for power and prestige. This period of growing European influence alongside the Empire's internal weaknesses and the rise of nationalist movements among its own subjects set the stage for the gradual disintegration of the once-formidable Ottoman Empire.