The awnser is a because it is the best awnser
Until recently, Sudan and South Sudan were a unified country. Africa is mainly known for its diversity of wildlife, but there is more to be known about this continent than its wildlife. There are certain political issues in some parts of the continent that require the world’s attention. Sudan and South Sudan are such parts of the continent which one should understand.
The thin outermost layer of the solid Earth is called the crust. The correct option among all the options given in the question is the second option. The crust actually accounts for less than 1 percent of the volume of the Earth. The Earth can actually be divided into four parts and they are crust, mantle, outer core and inner core.