The spatial diffusion of portuguese exploration in the 15th and 16th centuries can be traced most accurately by examining -
a. the trade of slaves, precious metals, and spices.
c. the spread of wars within africa.
b. the spread of christianity throughout asia.
d. the spread of navigation technologies throughout europe.

The spatial diffusion of these brave seamen who fared the sea in very dangerous times with very little technology can be best and most accurately examined by the trade of slaves, precious metals, and spices (a).

The reason a is the answer is because by viewing how this was being transported in the world, we can also see from which region to which region did they actually travel to. 

Possess private property.

The answer would be option a , b, and c.