Answer:
Why don't we have a complete fossil record of all life that's ever lived? Fossil formation requires a rare mix of physical and biological conditions. Fossils must be exposed at Earth's surface to have a chance of being found. Fossils can be destroyed when rocks erode, melt, or change composition.
Explanation:
For many reasons, the fossil record is not complete. Most organisms decomposed or were eaten by scavengers after death. Many species lacked hard parts, which are much more likely to fossilize. Some rocks and the fossils they contained have eroded and disappeared.
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Answer:
The right approach will be "Natural selection".
Explanation:
- Natural selection seems to be a mechanism that persists and reproduces populations of organisms that seem to be better suited to applications, however those that are somewhat properly equipped die away.
- This demonstrates that organisms that really can respond to a given climate can rise in quantities and therefore will ultimately outperform certain species that are unable to respond significantly.
Answer: 6 electrons
Explanation: Oxygen atom has atomic no of 8 which means it has got 8 electrons. n=2 depicts that the electrons have principle quantum no = 2. According to Afbau's rule the electrons are arranged in shells of increasing energy as follows:

Thus there are 2 electrons in 2s and 4 electrons in 2p which makes a total of 6 electrons.
The atom becomes positivly charged