A、About 4000 B.C. B、About 3000 B.C. C、About 5000 B.C. D、About 2000 B.C. B

The ancient Egyptians made many outstanding contributions in various fields. They created basic forms of math and a 365-day calendar. They invented a form of picture writing. They also invented a paper like writing material made from the stems of plants. The Egyptians were also great advanced in the development of sailing ships and barges.
    In ancient Egypt and certain other regions, the people made their first rafts of bundles of reeds. In time,(20)the Egyptians learned to lash bundles of reeds together to make boats that had a spoonlike shape.
    By about 4000 B.C., they had learned to build long, narrow boats powered by a row of people. During the next 1,000 years, the Egyptians made two more great advances in the development of ships.(21)By about 3000 B.C., they had discovered that sails could harness the wind and propel their boats.
    In addition, the Egyptians had learned to build boats out of planks of wood. After people knew how to make plank boats, they could even build ships—vessels that are big enough to cross the oceans.
    The ancient Egyptians designed many kinds of vessels. Their most outstanding achievement was probably the huge barges that carried enormous stone pillars from quarries up the Nile River. The biggest barges measured more than 200 feet long and carried 750 short tons of cargo.