I think the correct answer would be A. The yolk sac becomes the placenta. It is membranous sac that is attached to the embryo. It provides all the nutrition and the blood cells needed by the embryo. It is also called the umbilical vesicle.
1) The first stage of mitosis is actually just the condensing of the chromosomes.
2)They start out as double, then gradually get to the same number.
3)Cell actually spend the most time in the G phase of the cell cycle.
Answer: Geologists and other Earth scientists use geologic time scales to describe when events happened in the history of Earth. The time scales can be used to show when both geologic events and events affecting plant and animal life occurred. The geologic time scale pictured below (Figure below) illustrates the timing of events like:
Earthquakes.
Volcanic eruptions.
Major erosion.
Meteorites hitting Earth.
The first signs of life forms.
Mass extinctions.
Explanation:
I am Guessing Sperm and egg
