Answer:
oxygen and silicon, both are common
2nd option
Heat could transfer from object A to B
The reason : higher kinetic energy means the particles in A are moving /vibrating faster. This is a reason due to hight temperature.
The moderator of a nuclear reactor is a substance that slows neutrons down. In traditional nuclear reactors, the moderator is the same thing as the coolant: it’s water! When fast neutrons strike the hydrogen atoms in H2O, they slow down a lot (like a billiard ball striking another). There are other good moderators like graphite, beryllium, and more.
<h3>What is
moderator ?</h3>
Other neutrons are released at extremely high speeds when an incoming neutron splits an atom's nucleus. A sustained chain reaction is achievable if at least one (on average) of these neutrons can be made to split another fuel atom. In fact, if a neutron is traveling slowly, fuel atoms (like uranium) are more likely to absorb it (see Figure 1). In order to make a chain reaction easier to achieve, moderators are used in many reactor designs.
Neutrons can be slowed down more effectively in some materials than others. Because of the rules of conservation of energy and momentum, a neutron (mass 1) colliding with a heavy nucleus like a fuel atom cannot significantly slow down (mass 235).
To learn more about moderator from the given link:
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Ocean acidification is occurring because excess carbon dioxide (CO2) in the atmosphere is being absorbed at the surface of the ocean at an increasing rate. This excess CO2 results in more hydrogen ions, which increases the acidity of the ocean.
The answer of the question is C. Magnetic fields