A. The onset of the menstrual flow
First of all, pterophyta have neither seeds nor flowers in the first place.. Angiosperms are flowers and are the most diverse group of land plants so I doubt they would be losing its seeds... Lastly gymnosperms are a group of seed producing plants.. According to what I just wrote, what do you think the answer is??
I am like 99% sure its organ , try that and see if it works :)