最低分 The lowest grade

"Professor, I did the best I could on this test. I really don't think I deserve a zero."
 
"Neither do I. But that's the lowest grade I'm allowed to give."

学生：“教授先生，我这次考试已经竭尽全力了。我真的觉得我不应该得零蛋。”

老师：“我也是。但是这已经是我能给的最低分了！”