Why were the egyptians able to grow two or three crops per year?

How does the parallax of a nearby object compare to that of an object farther away?

According to the earth science reference tables, during which geologic time period were the continents of north america,south america, and africa closest together?

Which ecosystem best fits the characteristics listed below? which ecosystem best fits the characteristics listed below? ii. seasonal migrations of millions of wildebeests, zebras, and elephants iii. large numbers of predators, such as lions iv. acacia trees and grasses a. the congo rainforest b. the african mangroves c. the serengeti grasslands d. the sahel