What Was the Apparent Motivation for the Turco-Mongolian Warlord Tamarlane

What was the apparent motivation for the Turco-Mongolian warlord Tamarlane to conquer vast areas of land?

A) He sought to enrich his personal wealth.
B) He wanted to gain personal fame.
C) He wanted to keep his army engaged in combat.
D) He did it just for the sake of conquest.
E) He wanted to accumulate large numbers of slaves.