Sometimes, inexperienced students will plagiarize unintentionally, and then be surprised when the teacher warns the unexpected papers or gives them the failing grade. The best way to avoid unintentionally plagiarizing is to be very carefully gathering your information as you take notes of books and magazine articles about the topic you 'ye selected. First, try to assimilate the information thoroughly; Secondly, write it down in your own words, this is called paraphrasing. If you do a good job of paraphrasing, you will capture the main idea from your source without actually using any phrases from it. Most of your notes should probably be paraphrases from it. However, occasionally, you may find something you wish to quote directly in your research paper. In this case, be sure that you'll copy the quotation precisely in your notes and enclose it in quotation marks. That way when you're finalizing your research paper, you'll be able to remember which of your notes are direct quotes. You can then incorporate proprietarily and give your original author proper credit.
What does the speaker warn the students against doing？

A. Stealing another person's ideas.
B. Handing in assignments late.
C. Sharing notes with someone else.
D. Gathering non-relevant materials.