How is the assignment being presented? If the assignment is in a PDF, you can use "Annotation" for students to complete the assignment while preserving the questions. If the assignment questions are in the assignment description, the students can still see them while entering answers in the Text Entry box. For some assignments, I do instruct students to copy and paste the questions in to the Text Entry box, but I don't know of a way to have this Text Entry pre-populated with the questions.