what causes black holes

The topic i picked for helium.com was what causes black holes. I learned some theories of how they where formed, The size and effects they have on near by objects. Also about the temperature and the fact that black holes are not really holes. Also some think that with enough energy you can make a self made black hole. The type of writing element they used was informative essay by giving information about a subject with correct facts and a good flow he also went into detail. For the worse rating essay he did not go into as much detail and it seemed he left out key points while giving some wrong information. This essay was short and more of just a little bit of background information without as good flow. He also used question marks and such in a essay. If i was writing it I would make sure to research all my facts and go into more detail. I would also leave out the question marks and go for better transitions.