Explanation
Down's Syndrome is caused by an extra copy of chromosome 21,
therefore the answer is D) Trisomy 21.
Individuals with Down's Syndrome have three copies of chromosome 21 instead of the typical two copies, which is also known as trisomy 21. This results in various physical and intellectual characteristics, such as a flattened face, short stature, intellectual disability, and a higher risk of certain health issues such as heart defects and leukemia.
