Answer: time
Step-by-step explanation:
University is significantly harder than high school as the concepts are explained in greater depth and a greater commitment is required by lecturers. At the same time however, lecturers, unlike teachers in high school, will not place pressure on students to perform. They must do this on their own.
This is why it is important that students study hard to understand concepts presented in their courses or they will fall behind. They should do the assignments handed to them on time and submit it in time to avoid making costly mistakes as these assignments not only help the student understand concepts better, they can also contribute to the student's grade.