Pretty sure its C. Because if you look it up it says that it <span>illustrate the complex relationships among economic, social, and environmental issues </span>
The Amazon River is the world's longest river, measuring 6 992 km.
The Volga river is the largest river in Europe, so that should be the answer.
Doldrums are caused by solar radiation from the sun. Because of this the sunlight beams warms the air and causes it to rise straight up instead of side to side (horizontally).
