Extra chromosome 'X' is present in which of the following cases?

Klinefelter's syndrome.

The correct answer is Option (3)- Klinefelter's syndrome.

Turner's syndrome -  AA + XO: Turner's syndrome is caused due to the absence of one of the X chromosomes, i.e., 45 with X0, Such females are sterile as ovaries are rudimentary besides other features including lack of other secondary sexual characters.

Down's syndrome -  Trisomy: Down syndrome results from an extra copy of chromosome 21, known as trisomy 21, where there are three copies of chromosome 21 instead of the usual two.

Klinefelter's Syndrome -  Karyotype of 47 ,XXY : Klinefelter's Syndrome is characterized by the presence of an extra X chromosome in males, resulting in a karyotype of 47,XXY.