Which of the following event could possibly have been a cause of the first spanish colony in the americas being established

In 1491, no European knew that North and South America existed. By 1550, Spain — a small kingdom that had not even existed a century earlier — controlled the better part of two continents and had become the most powerful nation in Europe. In half a century of brave exploration and brutal conquest, both Europe and America were changed forever.

What are they! i have no idea lol

(d) it was complex and capable of highly organized efforts.