A、It cost too much time. B、The walls were too hard to engrave. C、The drawings were too simple to recognize. D、It wasn’t portable

Written communication has been the center of civilization for centuries. Most of our important records are on paper. Although writing has been around for a long time, paper hasn’t.
    In fact, putting thoughts down in written form wasn’t always easy or practical. Early people discovered that they could make simple drawings on the walls of caves, which was a great place for recording thoughts, but wasn’t portable.
    Imagine spending hours scratching a message into a heavy clay tablet and then having to transport it. That’s exactly what the Sumerians did around 4000 B.C. Although this form of written communication was now portable, it still wasn’t practical because of its weight.
    For centuries, people tried to discover better surfaces on which to record their thoughts. Almost everything imaginable was tried. Wood, stone, ceramics, cloth, bark, metal, silk, bamboo, and tree leaves were all used as a writing surface at one time or another.
    The word "paper" is derived from the word "papyrus", which was a plant found in Egypt along the lower Nile River. About 5,000 years ago, Egyptians created "sheets" of papyrus by harvesting, peeling and slicing the plant into strips. The strips were then layered, pounded together and smoothed to make a flat, uniform sheet.