Although all of the choices are correct to some degree, Mansa Musa's pilgrimage to Mecca BEST illustrates his A) belief in the Islamic faith. B) position as the king of the Mali Empire. C) goal to coordinate the trans-Saharan gold trade. D) establishment of universities in the Mali Empire.

Indeed, all the answers are, to some extent, correct, but the most remarkable because it encompasses the reality of the other answers is  

B) his position as king of the Empire of Mali.

Explanation:

It is not possible to understand King (emperor) Musa's pilgrimage to Mecca without separating it from his status as the most powerful and richest king of his time.  

His abundant and very rich entourage, the fact that the pilgrimage lasted more than a year, the creation of a mosque every Friday throughout that same year, the establishment of trade routes and even the economic crisis that led to the Islamic holy lands due to the amount of gold he squandered among the needy, are some of the aspects derived from his condition, undisguised as the powerful king (emperor) of Mali.

a. competition between france and england for land and power