Final answer:
Writing was invented in ancient Sumer to meet the needs of economic development, trade, and temple taxes. The writing system, called cuneiform, involved using a stylus to create wedge-shaped characters in wet clay. This system allowed the Sumerians to record various aspects of their society, including laws, religious texts, and commercial exchanges.
Step-by-step explanation:
Economic development, trade, and temple taxes drove the need to invent writing. Sumer had a writing system in place sometime between 3100-2900 BCE. Writing was done with a stylus in wet clay. As a result, the shape of the characters tended to be in the form of a wedge. When Sumerian writing was first discovered in the 19th century, it was called cuneiform, which means wedge-shaped. Hence, the answers to the blanks in your question are cuneiform for the system of writing, stylus for the instrument used, and cuneiform once again for the wedge-shaped writing.