Match List I with List II List I (Genetic disorders) List II (Type)...

Thalassemia is an autosomal recessive blood disorder, which is classified as a Mendelian disorder. Thus, (A) matches with (IV).

Turner's syndrome is caused by the absence of one of the X chromosomes, resulting in a karyotype of $45$, X0, which is an X-monosomy. Thus, (B) matches with (I).

Klinefelter's syndrome is caused by the presence of an additional copy of the X-chromosome, resulting in a karyotype of $47$, XXY. Thus, (C) matches with (II).

Down's syndrome is caused by the presence of an additional copy of chromosome number $21$, known as $21^{st}$ Trisomy. Thus, (D) matches with (III).

The correct matching is (A) - (IV), (B) - (I), (C) - (II), (D) - (III).

Answer: (A) - (IV), (B) - (I), (C) - (II), (D) - (III)