The age of exploration was the result of:

new luxuries brought home by the crusaders that caused a demand for new and better trade routes
new information and wealth brought from china by polo
new instruments and better methods of travel provided by prince henry's school of navigation
all of the above

all of the above

Explanation:

The age of exploration was prompted simply by the desire for better and free trade routes toward Asia as it provided lot of products that were attractive, high in demand, and brought lot of profit. The Ottoman Empire was huge problem in all of this as it managed to occupy the most important part of the trade route between the two continents, and in order for the others to use it demanded high taxes. With the improved technology and desire for wealth, the Europeans started to sponsor expeditions. While some managed to find routes to Asia by going around Africa, some ended up discovering two new continents, which marked the beginning of the European imperialism.

the answer is a. harriet tubman was a nurse on the battlefield.

a stronger central government  

its what they are