<u>Answer</u>:
Option 1.Eukaryotic cells first seen
Option 5. oxygen builds up in the atmosphere
<u>Explanation</u> :
- The name <em>Proterozoic eon</em> is derived from a Greek word which means earlier life.
- This eon represents the time just before complex life started proliferating on earth.
- One of the most important events that took place during this eon was <em>build up of oxygen in the atmosphere</em>.
The fossil evidence also shows the occurrence of <em>advanced single-celled eukaryotes.</em>
<em>So the events that define the Proterozoic eon are eukaryotic cells first seen and oxygen build up in the atmosphere. </em>
The water bends everyone's path into a normal line drawn perpendicular to the shoreline, as the people still on the shore are bent farther away from the shoreline than those in the water.
The same thing happens to a ray of light as it moves from air to water, or from a fast medium to a slow
one: it bends toward the normal.
Light does just that when moving between media. It takes the path that takes the least amount of time when you consider the difference in speed between the media.
For example, imagine you are looking out the window. You have air, glass, and then air again. Glass is denser than air, so light from the outside travels from a fast medium, through a slow medium, and back into a fast medium. The light takes its way from the outside to your eye, which spends the least time
learn more about refraction below
https://brainly.in/question/1651781
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I think the organisms are compared to each other.