Which of the sample(s) shown below is/are eukaryotic (with nucleus although some times they lose their nucleus like red blood cells)?

the correct option is option d

the menstrual cycle – higher tier. negative feedback mechanisms affect the production of hormones in the menstrual cycle. oestrogen also stimulates the release of lh (luteinising hormone) from the pituitary gland, which in turn controls the production of progesterone.

not too sure but maybe in the hot springs.