The correct answer is: A) Early 20th century
The formation of labor unions in Karnataka gained momentum during the early 20th century. The first labor union in Karnataka was formed in 1908, and by the 1920s, there were several unions representing workers in different industries. The unions played a significant role in the struggle for independence, and after independence, they continued to fight for better working conditions and wages for workers.
Option B, the post-independence period, is incorrect because the first labor unions in Karnataka were formed before independence.
Option C, the 1990s liberalization era, is incorrect because the labor unions in Karnataka were already well-established by the 1990s.
Option D, the 18th century, is incorrect because there is no evidence of labor unions in Karnataka during this time period.