Which of the following is the best reason for writing notes from research in your own words?

There are multiple reasons for this, when writing notes for research if you are writing them in your own words, you are thinking about how the subject works. You can copy text easily but putting it into different words that are your own help you understand the subject  will make it stick with you. 

The best reason is that you'll avoid plagiarism and then you also can tell that you have an understanding of the material.

I hope I've helped!