I'm not sure about the first two but I think the one about the halite crystal is cubic. :)
Answer:
magnetic and electric fields are applied perpendicular to each other
Microwaves are electromagnetic waves which are composed of magnetic and electric fields oscillating perpendicular to each other.
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D) Lesser amounts of fresh metals would be needed.
Answer:
The correct answer is A. Fossil fuels are cheaper than alternative forms of energy
Explanation:
Fossil fuels are made from organic matter of dead animals and mainly plants who were buried in the soil over hundred and thousand of years. We use fossil fuels because they are the best source to provide energy in the current time.
Fossil fuels are easily available and are present in very large amount which is the main reason for it to be cheaper. Fossil fuels like coal, petroleum or natural gas are more cheaper and efficient than alternative forms of energy like solar or wind energy.
But in future these fossil fuel will not be there and alternative forms of energy will become the primary and cheaper source of fuel.