The selling of indulgence was a major cause of the

Protestant reformation

Explanation:

In the late fifteenth century, a major world power that established colonies in the era of Old Imperialism was SPAIN. Their colonial activity was mainly limited to THE AMERICAS.

After the discovery of America in 1492, Spain explored and conquered large tracts of territory in the Americas, from the present southwestern United States, Mexico and the Caribbean, to Central America, most of South America and the northwest coast of North America.