Question 1044173
Assuming I interpret the question properly, line 1 is the first line where she goes astray.  The question is probability, and she begins with a combinatorial.  She has to begin with something probabilistic, and one way to do that is to say it is a probability of 1 over a combinatorial.

Also, physics wasn't included in the list.  This was probably a typographical mistake, but if not, then line 1 is the first combinatorial with a 6, where it should be a 5.