C
Explanation:
This is because the other variables in the other choices are relative to different observers and hence are not good to use in an experiment because there will be a lot of inherent bias by the person conducting the experiment For example how one person views how strong or beautiful the maple or oak looks may be different from how another person perceives the same.
However, weight is an absolute SI unit and does not vary from experiment to experiment. It is, therefore, a non-biased variable to use in the experiment and determine which wood between oak and maple can hold more weight.
Radio waves in a vacuum travel at the speed of light because they are a type of electromagnetic radiation like a light has been measured as traveling at 3×10^8 m/s in a vacuum.
Charged particles that are accelerating, like time-varying electric currents, are what produce radio waves. Radio and television signals are transmitted using radio waves, and microwaves used in radar and microwave ovens are also radio waves. Radio waves are emitted by a lot of celestial bodies, including pulsars. High RF exposure levels have the potential to heat biological tissue and raise body temperature. The body's inability to handle or remove the extra heat that could be generated by high RF exposure in humans could result in tissue damage.
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Gravity is often assumed to be the same everywhere on Earth, but it varies because the planet is not perfectly spherical or uniformly dense. In addition, gravity is weaker at the equator due to centrifugal forces produced by the planet's rotation
Wavelength is measured in various units of distance (mm, cm, m, etc.). Frequency uses hertz, but that is not what the question is asking. Therefore, the answer is false.