Who is the "they" referred to in the following quotation? They also established a number system based on six, dividing the hour into 60 minutes and the circle into 360 degrees, as we still do today.

b. The Sumerians.

Explanation:

The numbering system of dividing an hour into sixty minutes with 60 as the base was first founded and used by the Sumerians. It also included the description of the circle into 360 degrees. And this system was then passed down to the Babylonians.

The system which is also known as the sexagesimal system first originated in the ancient Sumerian civilization during the 3rd millennium B.C when the need to count to a number more than the fingers can account for arose. Then this process of numbering or counting was then passed on or adopted by the Babylonians and then with minor changes passed on to further generations and civilizations. This system became the inception of the numbering process which is still used to this day.

i think the answer is c, rivers.

explanation:

sometimes, borders fall along natural boundaries like rivers or mountain ranges. for example, the boundary between france and spain follows the crest of the pyrenees mountains. for part of its length, the boundary between the united states and mexico follows a river called the rio grande. the borders of four countries divide africa’s lake chad: niger, chad, cameroon, and nigeria.