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There are a number of reasons why the earth is more habitable than other planet and I'll list them out and try to explain them as best as I can.

1. The earth is located in what is referred to as the habitable zone. It isn't too close to the sun and it isn't too far from it. If it shifter by an inch either way, it would either become too hot or too cold.

2. The abundance of carbon, oxygen and water which are the building blocks of life. Carbon which is found in just about every life form on earth is present and easily bonds with other elements available. Oxygen is present which lets human beings breathe. Water which no life form on earth can live without is also present.

3. The earth's insulating atmosphere protects the planet from the harmful electromagnetic radiation of the sun.

4. The earth recycles everything and as such nothing is truly ever wasted, everything that is used up goes back to the earth in one way or another and this has helped sustain life on earth.

I hope this answers your question.

The truth is there are a lot of things that are present in the earth that humans need which are totally absent in other planets. One important thing is the intensity of sunlight that we receive. Earth is placed in a distance that humans get the enough temperature we need from the Sun. Imagine if Earth is put in Mercury.

Second is the presence of our atmosphere. Earth is only the planet that has the atmosphere suitable to humans. With its layered structure, without it the earned should've been dead.

Third is the presence of oxygen that human needs. Oxygen is the most important element for our breathing and that without it, humans simply can't exist.

Fourth, is the presence of freshwater which is the most suitable liquid that helps our body circulate and activate. 

Lastly, planet Earth has the ability to cycle everything so that it is sustainable. A cycle and process are done in all matter, that's why Earth is still living and functioning as a planet suitable for humans. 

The presence of water and oxygen. supports life forms. The earth is far enough away from the sun that it doesn't do damage and is bearable.