Cri-du-chat syndrome in humans is caused by the

The correct option is D Loss of half of the short arm of chromosome 5

• Trisomy of 21st chromosome causes down syndrome. Three copies of the chromosome (due to nondisjunction) are found in the embryo instead of the usual two.
  
• Fertilization of an XX egg by a normal Y sperm cause Kleinfelter's syndrome that produces womanly features in a man.
• Cri-du-chat syndrome occurs due to loss of half of the short arm of chromosome 5. This syndrome is named so due to the characteristic cat-like cry of the affected children.

So. the correct option is 'Loss of half of the short arm of chromosome 5'.