Answer: Option A "Choroid plexus".
Explanation:
Cerebrospinal fluid can be defined as the fluid that is found in the brain and spinal cord of human beings. It is a clear and colorless fluid.
The production of cerebrospinal fluid takes place by the specialized ependymal cells that lies in the choroid plexuses which is present in the ventricles of brain.
The amount of cerebrospinal fluid in a day is 500mL. This fluid acts as cushion that protects the brain from mechanical and immunological protection.
Hence, the correction answer is option A
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Smog is an abiotic factor affecting a biotic factor(s).
This is because smog isn't a living organism so it is abiotic while humans are multicellular organisms so therefore, they are biotic factors.
Smog has a negative effect on many biotic factors.
