题目

Botswana lies immediately to the north of South Africa. It is bordered on the north and west by Namibia, on the north and east by Zimbabwe, and is connected by a narrow strip of land on the northern border to Zambia. Its territory consists almost entirely of a broad, flat, arid subtropical plateau(高原), though there are hills in the eastern part of the country. In the northwest, the Okavango River empties into the Kalahari sands, creating the largest inland river delta in the world. While the Okavango Delta is home to relatively few large animals in comparison to other areas of Botswana, it由抛物线y＝x2－x，直线x＝－1及x轴围成的图形的面积为（ ）A． B．1 C． D．