To find the number of puzzles one student would complete, we can divide the total number of puzzles completed by the number of students. So, if 80 puzzles were completed by students, and we have 1 student, we can divide 80 by 1 to get 80 puzzles per student. Rounding to the nearest tenth, the answer would be 80.0. Therefore, the correct answer is D) 15.0.
