How many districts are there in Terai region of Nepal?

Option D

Terai is a low land region containing some hill ranges. Looking out for its coverage, it covers 17% of the total area of Nepal. There are 21 districts in terai region of Nepal. The Terai (also spelled Tarai) region begins at the Indian border and includes the southernmost part of the flat, intensively farmed Gangetic Plain called the Outer Terai. By the 19th century, timber and other resources were being exported to India. Industrialization based on agricultural products such as jute began in the 1930s and infrastructure such as roadways, railways and electricity were extended across the border before it reached Nepal's Pahad region.