Please select the word from the list that best fits the definition the bond of loyalty between a lord and a vassal

loess contribute to the flooding of rivers by providing the silt that is washed into rivers and constantly raises the bed of the rivers. this elevation above the surrounding flood plains and dams allow the river to overwhelm the dams and flood thousand of square miles of neighboring flood plains.

can you explain it better

the answer is a. monarch

the correct answer is the following is a list of inventions made in the medieval islamic world, especially during the "islamic golden age" (8th to 13th centuries),[1][2] as well as the late medieval period, especially in the emirate of granada and the ottoman empire.

science and technology in the islamic world adopted and preserved knowledge and technologies from contemporary and earlier civilizations, including persia, india, china, and greece-roman antiquity, while making a number of improvements and innovations.