Answer:
B. About life in the Empire of Mali.
Step-by-step explanation:
Option A is not correct as Ibn Battuta lived and wrote in 15th century, while Roman Empire collapsed in the 5th Century.
Options C and D are not correct as we no details of that in his writings.
He didn't visit Mali during Musa's reign, but later during the reign of Suleyman Keita and was able to see how life functioned in this kingdom.