7 Thanks to Ibn Battuta's writings, we know:
A
How the collapse of the Roman Empire threw Europe Into
the Dark Ages
B.
About life in the Empire of Mall
C
That many librarles and mosques bullt under Musa still
stand today
D
How Musa I bullt embassles abroad

B.  About life in the Empire of Mali.

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.