Freshwater ecosystems that often originate from underground sources in mountains or hills are a estuaries. b rivers and streams. c lakes and ponds. d wetlands.

Option B, rivers and streams

Explanation:

Lakes and ponds are water bodies that hold water with in them and remain stagnant. The major source of water for these water bodies is rainfall.

Wetlands are forest areas that have water quantity enough to surpass the absorption capacity of soil thereby causing water logging.

Estuaries are areas lying just before the convergence of fresh water bodies into the ocean.

hence, the correct option is B

the earth is thought to have been formed about 4.6 billion years ago by collisions from a cloud of hydrogen, helium, rock, ice and other materials. these were pulled together by gravity to form objects in and around earth like- asteroids and small early planets called planetesimals.

so, the best possible answer to this question will be option d- to harden materials to form different parts of earth’s layers