15. Even though sub-Saharan Africa often evokes images of drought and famine, researchers say that the area is the home of more than 2,000 grains, vegetables, roots, fruits, and other foods that have the possibility for feeding the continent, even other parts of the world.
(E) could possibly feed the continent and, in addition, for even
答案是D，没有异议，但是为什么这里用could啊？句子的整个时态都是一般现在时啊？