Northern china built the great wall to protect itself from the invasions of the (touman, xiongnu, saka, scythian.) nomads?

The correct answer is Xiongnu

This was a tribe of Mongolian people that constantly fought wars with northern China. Touman was a a ruler of one of the tribes who became so important that he became the ruler of all the tribes which was called a chanyu. The wall was built to protect from entering China.