Natural selection is best described as: Isolating the species so that they no longer experience competition with other species
The ability to spontaneously generate new traits that better suit the species
Increasing the perfection of the species
Passing on existing variation of traits to favor those that are better suited to an organism's environment.

d i think its   answer d

"menstrual cycle is a complex cycle that consists of several processes. order of occurrence of steps in menstrual cycle are as follows:

1. high progesterone levels maintain the endometrium lining of the uterus.

2. endometrium lining breaks down and low levels of estrogen stimulate the pituitary to release fsh and lh.

3. fsh and lh stimulates the follicles to develop and the oocyte to produce estrogen.

4. rising estrogen levels suppress fsh production and development of other follicles.

5. a spike in lh causes follicle to rupture.

6. a breakdown of corpus luteum causes progesterone level to drop."

if your own plato the answer is b. the fern transitioned from sporophyte generation to gametophyte generation.