Answer: d- because a model is never exactly the same as the thing it represents
Answer;
-PET scan
A PET scan uses radioactive markers in the blood to monitor blood flow and metabolic activity via x-ray
Explanation;
-A positron emission tomography (PET) scan is an imaging test that helps reveal how the tissues and organs are functioning. A PET scan uses a radioactive drug (tracer) to show this activity. This scan can sometimes detect disease before it shows up on other imaging tests.
-A PET scan is used to diagnose certain health conditions, to plan treatment, to find out how an existing condition is developing, and to see how effective a treatment is.
-In a PET scan, a machine detects radiation that is emitted by a radiotracer. A radiotracer consists of radioactive material that is tagged to a natural chemical, such as glucose.
It is intercepted first by the atmosphere, a small part of the sun's energy is directly absorbed, particularly by certain gases such as ozone and water vapor. during the day the sun shines through tha atmosphere <span>
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