Answer !
what is a mutation?

(a)any change in a gene or chromosome
(b)any change that is harmful to an organism
(c)any change that is to an organism
(d)any change in the phenotype of a cell

you dont brother god luck

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.

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.