题目解析：
【题目翻译】根据第3段，舌蝇在东部和中部非洲的存在导致下列哪一个？
A：撒哈拉以南非洲地区的人们开始把更多的精力放在种植谷类作物上，而不是养活牲畜上。
B：邻近的牧民的袭击急剧增加。
C：牧牛人向南散布，在没有舌蝇的地方放牧牲畜。
D：大多数狩猎-采集组织将他们的食物收集限制在撒哈拉以南无舌蝇的地区。
【判定题型】：题目问的是文章中的具体细节信息，故根据题目问法可以判断本题为事实信息题。
【关键词定位】根据题干中的关键词“tsetse fly”，可以定位到第三段倒数2、3、4句“At the same time, the cattle owners had to graze their stock in tsetse-fly-free areas ……As a result, small cattle herds spread south rapidly in areas where they could be grazed.”
【逻辑分析】题目问，在东非和中非的舌蝇会造成什么后果？这三句话的内容都是在讲舌蝇和舌蝇带来的后果。题干中“caused”一词是在问结果，所以我们在文中找到关键词“as a result”，后面的内容就是结果，即小部分牛群迅速地向南部地区迁移，在那里人们可以放牧。
【选项分析】
A选项：撒哈拉以南非洲地区的人民开始花更多精力培养谷物，而不是饲养牛群。错误，因为文中没有提到两者之间的比较关系，人们即种植谷物，也饲养牛群。其次，这不是舌蝇造成的影响。
B选项：邻里之间抢夺牛群的情况愈演愈烈。对应第三段最后一句“Long before cereal agriculture took hold far south of the Sahara ……by gift exchange or through raids on herding neighbors.”但是这句话只是为了说明狩猎采集者获得牲畜的方式——作为礼物交换，或者通过劫掠放牧的邻居来获得这些牲畜。这并不是舌蝇造成的影响。故B选项排除。
C选项：正确表达了原文的意思，所以C选项正确。
D选项：大部分的狩猎采集者将他们的觅食范围限定在了撒哈拉南部没有舌蝇的地带。错误，因为文章没有提到该信息。
At the end of the Pleistocene (around 10,000 B.C.), the technologies of food production may have already been employed on the fringes of the rain forests of western and central Africa, where the common use of such root plants as the African yam led people to recognize the advantages of growing their own food. The yam can easily be resprouted if the top is replanted. This primitive form of "vegeculture" (cultivation of root and tree crops) may have been the economic tradition onto which the cultivation of summer rainfall cereal crops was grafted as it came into use south of the grassland areas on the Sahara's southern borders.
As was the case elsewhere, cattle were demanding animals in Africa. They required water at least every 24 hours and large tracts of grazing grass if herds of any size were to be maintained. The secret was the careful selection of grazing land, especially in environments where seasonal rainfall led to marked differences in graze quality throughout the year. Even modest cattle herds required plenty of land and considerable mobility. To acquire such land often required moving herds considerable distances, even from summer to winter pastures. At the same time, the cattle owners had to graze their stock in tsetse-fly-free areas The only protection against human and animal sleeping sickness, a disease carried by the tsetse fly, was to avoid settling or farming such areas - a constraint severely limiting the movements of cattle-owning farmers in eastern and central Africa. As a result, small cattle herds spread south rapidly in areas where they could be grazed. Long before cereal agriculture took hold far south of the Sahara, some hunter-gatherer groups in the savanna woodlands of eastern and southern Africa may have acquired cattle, and perhaps other domesticated animals, by gift exchange or through raids on herding neighbors.
