An astronaut is stationary in space. which of these would have the greatest speed as observed by the astronaut? a: a ray of visible light b: a strong magnetic field c: a high speed electrical charge d: a longitudinal wave carrying sound

A: a ray of visible light  

Explanation:

Light is an electromagnetic radiation. It can travel through vacuum as well as medium. The speed of light is maximum in vacuum i.e. 3 × 10⁸ m/s. From experiments, scientists know that nothing can exceed the speed of the light i.e this speed of light is the upper limit and o particle or wave can travel with speed greater than this. Thus, a ray of visible light would have the greatest speed when observed by an astronaut.

the skeletons of most mammals reach a certain size and then stop growing. however, many animals, including some mammals, keep growing throughout their lives. kangaroos, for example, just keep growing and growing until they die. also, the longer an animal lives the greater the chance it might catch some deadly disease.

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