Why does the author use an intensive pronoun in this passage?

Ais a group of individuals of the same that exist in the same place at the same time

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.

L2.4.3 test (cst): the story question 13 of 20 2 points choose the sentence that uses parallel structure correctly. o a. not only is she cutting her hair, but also coloring it. o b. he either decided to run the race or volunteer. o c. i am not only baking cookies but also brownies. od. neither my mother nor my father can watch my game.