Answer: American sports culture has a much greater appreciation of and emphasis towards collegiate and high school sports. This may be the strongest difference between American sports culture and every other countries' sports culture.
The movement of the tectonic plates is caused by convection currents in Earth´s mantle.
Answer: A) convection currents in Earth´s mantle.
You would know a decomposition reaction occurred if the reactants separated. For example from AB → A+B.
Now if you look at your options only 1 works out for that equation. Letter A.
From the compound K2CO3 it split up to K2O +CO2
It cannot be letter B because synthesis/combination occurred. The same goes for letter C. Letter D, single displacement occurred.
Again, the answer is A.
The density of seawater at a depth where the pressure is 500 atm is 
Explanation:
The relationship between bulk modulus and pressure is the following:

where
B is the bulk modulus
is the density at surface
is the variation of pressure
is the variation of density
In this problem, we have:
is the bulk modulus

is the change in pressure with respect to the surface (the pressure at the surface is 1 atm)
Therefore, we can find the density of the water where the pressure is 500 atm as follows:

Learn more about pressure in a fluid:
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Position 1 I believe because that is when the potential energy is released on the downfall