Why a seemingly open curve is identified as closed curve by rhino?

as shown in the screenshot, this curve seems open but Rhino says it’s closed…
Why is that? How can I modify it to open curve?

It’s probably overlapping on itself. Explode it and see what you get.

Ahh! Thanks a lot, Jim! They are overlapped!

Hi Wally - you can use ShowEnds to display the start and end points of curves.