There is trisomy of chromosome $13$ which is characterised by mental retardation, sloping forehead, deformed face, polydactyly, cardiac defects, etc. The syndrome is?

The correct option is B Patau's syndrome

• Klinefelter syndrome is a genetic condition in which a male is born with an extra copy of the X chromosome. it also called XXY syndrome.so its an x chromosome aneuploidy.
• Edward's Syndrome is an trisomy of chromosome 18, it is a chromosomal abnormality that often results in stillbirth or an early death of an infant.
• Turner syndrome is a chromosomal condition that affects development in females. In which a female is born with only one X chromosome ( 44+ XO).
  
• Patau's syndrome is trisomy of chromosome 13.
  So, option B is correct.