Explanation:

The First Anglo-Afghan War took place from 1839 to 1842. This period falls squarely within the 19th century, which spans from 1801 to 1900. Therefore, the war was fought in the middle of the Nineteenth Century. Option (A) Sixteenth Century refers to the period 1501-1600, which is incorrect. Option (B) Seventeenth Century refers to 1601-1700, also incorrect. Option (C) Eighteenth Century refers to 1701-1800, which predates the conflict. Thus, only the Nineteenth Century aligns with the historical timeline of the war.