1. Which force was the first to be discovered? A. Gravity B. Weak nuclear forces C. Strong nuclear forces D. Electromagnetic force
2. What two qualities of objects does gravity depend on?
A. What each object is made up of and the distance between them
B. What each object is made up of and the material between them C. Each object’s mass and shape
D. The mass of objects and the distance between them
3. An asteroid flies close to the Earth. Gravity–
A. repels the asteroid away from Earth.
B. attracts the asteroid and Earth to each other.
C. makes the asteroid spin rapidly. D. causes the asteroid to explode.
Gravitational Forces (C)
3

b.

explanation:

2b2t

explanation:

2b2t

bacteria that live on the ocean floor are sustained by phytoplankton. phytoplankton, microscopic marine photosynthetic organisms, have a vastly significant role to play not only in the marine food web of which they’re part of, but also on a more global scale. despite their infinitely small size in comparison to other marine organisms, these tiny creatures occupy an immensely important ecological niche: they are the foundation of the marine food web, and as primary producers, play key roles in supporting all other organisms in the marine environment, as well as in the regulation of the earth’s climate through the sequestration of carbon, oxygen production, and other related processes. phytoplankton account for roughly half of all global primary productivity; therefore, their significance extends far beyond the marine environment alone. there is an intriguing sense of irony in the realization that these tiny living beings that often live out their existence unnoticed and undetected by the rest of the world, have such a far-reaching impact on the lives of virtually all other living organisms on the planet, particularly on those in the marine environment. the world that we have become accustomed to has been and is continuously shaped by the workings of these miniscule yet vital “plants of the sea”.

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