The correct option is A Aneuploidy
The chromosomal disorders are caused due to lack or additions or abnormal arrangement of one or more chromosomes. Failure of segregation of chromatids during cell division cycle results in the gain or loss of chromosome(s), is called aneuploidy. For example, Downs syndrome results due to gain of extra copy of chromosome 21. Similarly, Turners syndrome results due to loss of an X chromosome in human females