Complex systems of written characters were developed in the huang he and yangtze river valleys a. by the sumerian civilization b. by the ancient egyptians c. by the toltec civilization d. during the shang dynasty

The answer would be during the Shang Dynasty because these two valleys are in China.

D. during the Shang dynasty.

Explanation:

The Shang dynasty is a chines dynasty that was ruled over the area of lower yellow river systems and is also called as Yin dynasty and developed in the second millennium BC, succeeded by the Xia dynasty. And is approx 2,000 years old, and was ruled from the  1766 to 1122 B.C. The Anyang site is known as the oldest known body of the Chinese written languages and has most of the divine inscription in the oracle bone and the turtle shells, with more than 20,000 discoveries made in the 1930s. with an area of about 1,250,000 km square. The oldest known records exist of approx 1200 B.C with at least nine Shang kings. And their writings were preserved the bronze inscription.

Answer volcanic eruptionsseismic waves from earthquakes;