Question from Alison's math test

OK, so I'm a math geek. But Ali showed me this from her recent math test and said that her teacher said that hers was OK, but the red one he drew was better. After making sure she understands the concept (she does) I *love* her line (and think it's better!)

(Note for non-math-geeks ... the arrow at the end means it goes... on forever, so EF goes on forever in both directions, but HG starts at H and only goes on forever towards G and beyond)