The striking molecular similarities that exist between earth's many diverse species can best be explained by a. random changes that occur separately in each species' genetic code. b. the sharing of common ancestors within the species' evolutionary history. c. the inability of the species to undergo evolutionary change over time. d. species mating with other species to produce offspring.

B

Explanation:

While we may have many species on earth, they all share a common ancestor known as the cenancestor. Even when comparing the genomes of many different species on earth, these are a number of genes (approximately 300) that have been conserved throughout these species some of these being associated with cellular respiration and central dogma.

"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."