The correct answer is option 3: Britain.

In the nineteenth century, several European countries engaged in colonial expansion, seeking to establish colonies and exert control over other parts of the world. Out of the options provided, Britain emerged as the biggest colonial power during this period. Britain`s empire spanned across several continents and included territories such as India, Canada, Australia, and parts of Africa. The British Empire was known for its vast resources, economic influence, and military strength. Their colonial rule often involved the exploitation of resources and the imposition of British culture and administration on the colonized nations. While France, Spain, and Germany were also engaged in colonial activities during this time, they did not have the same extent of colonial holdings as Britain.