The largest and most important river system in South America is the Amazon. Making A your answer.
Gravity keeps the water and yourself from falling off the planet into space.
Yes, organic material in soil is more productive.
In the absence of any forces, no force is required to keep an object moving. ... Skipping Newton's second law (arguably the most important law for our purposes ) for ... mean that the movements are equal (or that the objects will stop moving). .... However, if we had forgotten to reset acceleration to zero, the gust of wind would ...