Hi Jorma Spitz,
First of all, a warm welcome to CodeRanch!
Jorma Spitz wrote:It sais the argument on line 18 is a short. But the short is on line 17. (The ebook is correct on this one)
You are correct!

The first sentence of the explanation of the online test should be: "
The argument on line 17 is a short.".
It's strange that this typo doesn't occur in the eBook, nor the paper book; but does occur in the online test.
Hope it helps!
Kind regards,
Roel
PS. Have a
cow for spotting (and reporting) this typo!