Answer:
Mental rètàrdation caused by what Deficiency
Trisomy 21, also known as Down syndrome, is the most common genetic cause of mental rètàrdation.
Causes of mental rètàrdation include fetal alcohol syndrome and fetal alcohol effect; brain damage caused by the use of prescription or illegal drugs during pregnancy; brain injury and disease; and genetic disorders, such as Down syndrome and fragile X syndrome.
Explanation:
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