But I had to laugh as the author asks in the article:
> What kind of horrible graph is this?
The wrong one. He should have used a bar chart instead of this line chart. Doesn't change the content and meaning of the chart, but actually makes it accurate and readable as the data it not about the relation between the number of students that got these marks but actually about the number of students that got these marks. A bar chart is much better to show that.