One of the challenges of studying life from ancient times is that not all organisms form fossils. Which of the following explains why some organisms form fossils and others don't. (Select all that apply)

a. The tracks or burrows of an organism must be filled with sediments before they are disturbed.

b. The organism must first get stuck in rock.

c. The soft tissue of the dead organism must be eaten by scavengers or decomposers before the bones can be preserved.

d. The organism's body must be covered by sediment or another substance before its body decays.

"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."

the answer is c. it will give up it's valence electron to the other atom.