3. Read these sentences from the article. "I've often wished that I had a time machine to go back and collect a sample of ancient
atmosphere or an ancient bit of seawater," says (Jay] Kaufman. "But we can't. All we
can do is collect rocks that were formed under those waters and under that
atmosphere."
Which conclusion does this statement support?
A. Scientists are skeptical about their ability to determine when oxygen levels in the
Earth's early atmosphere rose.
B. Scientists are unable to study what the Earth was like millions of years ago because
they do not have the materials needed to do so.
C. Scientists study the atmosphere in order to learn what the Earth's seawater was like
millions of years ago.
D. Scientists study rock formations in order to learn what Earth's atmosphere was like
millions of years ago.

the atomic number of magnesium is 12. its nucleus must contain 12 protons and no electrons. the atomic number of an atom is determined by the number of protons.

magnesium is an electrolyte injection commonly used to treat low magnesium levels in your blood. it is also used to prevent or control seizures in women with preeclampsia or eclampsia.

i believe it's c. the trait for large beaks will be passed on to future generations through natural selection.

since eventually smaller beaks would have to find another source of food or even eventually just die out from the lack of food.

the right is separation by density .

take the blood which is a good example of a heterogeneous mixture.

blood is a vital liquid in our body, which transports oxygen from the air to our lungs so we can breathe. it is also used to eject wastes, such as carbon dioxide, to bring cells and molecules of the immune system to the tissues, and to spread hormones throughout the body. it corresponds to plasma, red blood cells, white blood cells, platelets and hemoglobins combined.

in medical tests centrifugal force is used to separate the different components of the blood.

in general, the centrifugation will allow to separate and analyze the different components of the blood, to know if the rate of white blood cells in the blood of a patient, for example, is normal, and therefore to know if his system immune is integrity.

under the action of centrifugal force, the solid components in the blood are drawn to the bottom of the tube in which the blood is contained. the centrifugal force then acts as an accelerated settling. it separates plasma from red blood cells and white blood cells.