According to paragraph 3, recent research into the topography of the Memphis region in ancient times suggests which of the following? A. The level of the Nile floodplains was much higher in predynastic and dynastic times than in later times. B. The sediment deposits of wadis were not as noticeable in predynastic and dynastic times than in later times. C. The Nile valley at the point of Memphis was narrower in predynastic and dynastic times than it was in later times D. Frequent rainy periods may have caused a significant reduction of trade traffic during the predynastic and dynastic times.