In what way did climate change affect Ghana's position in the trans-Saharan trading networks?

In what way did climate change affect Ghana’s position in the trans-Saharan trading networks?

A. The larger floods of the Niger River made consistent trade impossible.
B. The rise in temperature in West Africa made insect-born disease more common.
C. The desertification of Kumbi Saleh made it less important as a trade post.
D. The rise in temperature made food production difficult for large kingdoms.