c$.$ What problems might African farmers have because they lack secure property rights?

A$.$ Without secure property rights, farmers in Africa may be reluctant to make the investments in their farms that would raise the farms' productivity.

B$.$ Without secure property rights, it is harder for farmers to borrow because they cannot use their land as collateral.

C$.$ Without secure property rights, farmers are not able to obtain funds by selling some of their land.

D$.$ All of the above.