Highlighting instead of hotspotting

Hi all.

I am working on a plagiarism test in which I am trying to create plagiarism detecting exercises for students. However, I find using hot spots less helpful to indicate a plagiarized part of a written work. The problem is that the student can show a plagiarized part of the text only by clicking on a word. But sometimes it is not just a word that is copied from somewhere else. It can be a whole sentence or a paragraph or a text. I want to let students fully highlight (with the cursor) the part of the text that they think is plagiarized. By this, they can easily show a word, a part of a sentence, a sentence, a paragraph that they think is plagiarism. So, does anyone have any experience of how to make it happen? Other creative ways of managing the plagiarism detecting exercises would also be very appreciated.