In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

Which of the following did not occur in the 20th century: urbanization, the spread of the Ottoman Empire, or wars?, Context: South Slavic historically formed a dialect continuum, i.e. each dialect has some similarities with the neighboring one, and differences grow with distance. However, migrations from the 16th to 18th centuries resulting from the spread of Ottoman Empire on the Balkans have caused large-scale population displacement that broke the dialect continuum into many geographical pockets. Migrations in the 20th century, primarily caused by urbanization and wars, also contributed to the reduction of dialectal differences.
spread of Ottoman Empire