题目解析：
【题目翻译】根据第3段，最近对孟菲斯地区古代地形的研究表明了什么？
A：尼罗河洪泛区前汛期和王朝时期的水位明显高于后汛期。
B：河底沉积物在前、王朝时期不如后期明显。
C：孟菲斯山顶的尼罗河谷在先秦和王朝时期都比后来窄。
D：频繁的雨季可能导致前王朝时期贸易量的显著减少。
【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】：根据关键词“in ancient times”,定位到Passage 3 第6句，原句为“When the floodplain was much lower, as it would have been in predynastic and early dynastic times, the outwash fans (fan-shaped deposits of sediments) of various wadis (stream-beds or channels that carry water only during rainy periods) would have been much more prominent features on the east bank. ”，意思是“当洪泛平原低得多时，如前王朝和早期王朝时期那样，各种洼地（河床或只在雨季运水的河道）的冲刷扇（沉积物的扇形沉积物）将会是东岸更加显著的特征。”。
【逻辑分析】根据时间关系来推断答案。
【选项分析】
A选项：尼罗河泛滥平原的高度在“predynastic and dynastic times”的时候要更高。定位到原文这句话“When the floodplain was much lower, as it would have been in predynastic and early dynastic times……”因此，我们可以知道在埃及前王朝时期和埃及王朝早期，泛滥平原的高度要低得多，故A选项与原文矛盾，排除。
B选项：相比后来，河流沉积物在“predynastic and dynastic times”这一时期更多，但文中并未提到这两个时间段河流沉积物的对比。文中只提到“much more prominent features on the east bank.”东岸的沉积物更多。故B选项文中未提及，排除。
C选项：尼罗河谷在“predynastic and dynastic times”这一时期更窄。对应文中这句话“The valley may have narrowed at this point to a mere three kilometers, making it the ideal place for controlling river traffic.”意思是这个山谷在当时变得很窄，宽度仅为3公里，这也使它成为了控制河流交通的理想地点。故C选项符合原文，正确。
D选项：频繁的降雨使“predynastic and dynastic times”的贸易交通减少。错误，因为文中并未提及。
The city of Memphis, located on the Nile near the modern city of Cairo, was founded around 3100 B.C. as the first capital of a recently united Egypt. The choice of Memphis by Egypt's first kings reflects the site's strategic importance. First, and most obvious, the apex of the Nile River delta was a politically opportune location for the state's administrative center, standing between the united lands of Upper and Lower Egypt and offering ready access to both parts of the country. The older predynastic (pre-3100 B.C.) centers of power, This and Hierakonpolis, were too remote from the vast expanse of the delta, which had been incorporated into the unified state. Only a city within easy reach of both the Nile valley to the south and the more spread out, difficult terrain to the north could provide the necessary political control that the rulers of early dynastic Egypt (roughly 3000-2600 B.C.) required.
Equally important for the national administration was the ability to control communications within Egypt. The Nile provided the easiest and quickest artery of communication, and the national capital was, again, ideally located in this respect. Recent geological surveys of the Memphis region have revealed much about its topography in ancient times. It appears that the location of Memphis may have been even more advantageous for controlling trade, transport, and communications than was previously appreciated. Surveys and drill cores have shown that the level of the Nile floodplain has steadily risen over the last five millenniums. When the floodplain was much lower, as it would have been in predynastic and early dynastic times, the outwash fans (fan-shaped deposits of sediments) of various wadis (stream-beds or channels that carry water only during rainy periods) would have been much more prominent features on the east bank. The fan associated with the Wadi Hof extended a significant way into the Nile floodplain, forming a constriction in the vicinity of Memphis. The valley may have narrowed at this point to a mere three kilometers, making it the ideal place for controlling river traffic.
