Which of the following actions shows an example of periodization?
a. dividing history into different eras, such as the iron age and bronze age
b. creating a timeline of the major events and battles of the american revolution
c. categorizing historical events by the geographical regions, such as europe and asia
d. comparing the political, economic, and social aspects of the united states and china.

The greatest gift the sumerians gave the world was the invention of writing. the sumerians were wealthy people. they needed some way to keep track of what they owned. they began drawing pictures. they used a reed as a pen. they drew on soft pieces of clay. the soft clay was then dried in the sun. the tablet became a permanent record. later, the sumerian drawings changed into wedge-shaped symbols. this kind of writing is called cuneiform. by putting symbols together, the sumerians could write entire sentences.