A shepherd takes his herd of sheep for grazing in a region with rocks, trees and long stretches of grassland. He used a stick that had a small iron piece attached at one end to control the herd. One day he noticed that the iron in the stick was attracted to a part of the rock. Which of these events explain the presence of a natural magnet?

Once an egg cell is fertilized by sperm, the cell then, as the embryo develops, it receives nourishment and eliminates wastes by transferring substances from its blood to its mother's blood. a. becomes a fetus immediately and exits the womb b. begins to divide and implants itself in the wall of the uterus c. remains in the uterus without dividing for several months d. travels back to the ovaries until the fetus is developed