The correct answers are:

C. spills from the nation’s oil production.

Nigeria is one of the leading oil producers in sub-Saharan Africa, but unfortunately, it is not taking cautions towards the protection of the environment. The oil spills are a common thing, and the only thing in mind of the companies is profit, so they are not fixing the problems, but instead, they are leaving it as it is, and the situation is worsening all the time.

B. desertification caused by poor agricultural practices.

The agriculture in Africa, especially in sub-Saharan Africa, in general, is still primitive, and people re not taking into consideration the land degradation that they are causing with their methods. One of the reasons is the poverty, so people only look short term, and try to profit as much as they can, though on the long run, they are destroying the land and inviting desertification, thus losing the land to profit from it.