They show that there was an ocean over the plains long ago, and fossils are always used to elaborate on the history of life/how it developed.
The answer is:
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[C]: Mercury and Venus.
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Mercury would be "Planet A"; and Venus would be "Planet B".
Plate tectonic is a scientific theory that says the Earth’s lithosphere is divided into several plates. The plates glide over the mantle. In early 20th century, this theoretical model builds on the concept of continental drift. It was first proposed by the scientist Alfred Wegener in 1912. After seafloor spreading was validated, the theory was accepted by the geoscientific community.
I think 2,5,1 but im not sure
A river's width and depth increases as more water is added from tributaries.