A river begins as a trickle of melting snow on a mountaintop, or as a spring of underground water, bubbling out from a crack in a mountain. The water finds its way down the mountainside, running over rocks. Farther down the mountain, it is joined by another little trickle formed by rainwater. Together, these tiny trickles make a wider, faster-moving stream. More and more trickles join the stream as they form a wide and fast-flowing river, rushing down the sloping mountainsides.
Once the river reaches the foot of the mountain, the land begins to slope and then flattens for several miles. This flattened land is called a floodplain as this is where a river bursts from its banks and floods the surrounding land in times of heavy and stormy rains. By now, the river is wider and its course is straighter. It widens even more as it approaches the sea, before finally emptying into the sea.
Some rivers flow for centuries, while some dry out due to harsh and dry summers and a lack of adequate rainfall. For example, Dry Falls, located in Central Washington, no longer carries water. The Colorado River flowing from the United States to Mexico, and the Indus River that runs from India to Pakistan, are both starting to dry out. On the other hand, rivers such as the Nile in Africa, the Amazon in South America, and the Yangtze in China have plenty of water and flow in abundance.
Which of the following relationships is most similar to the relationship below?
Melting snow : River
A.
Evaporating water : Rainfall
B.
Soil erosion : Mountains
C.
Mountains : Tall trees
D.
Floods : Rainwater