To solve this problem, we need to match the conditions in List I with their corresponding chromosomal associations in List II. Let's analyze each condition:$\newline \bullet$A. Down's syndrome:$\newline$Down's syndrome is caused by trisomy of the 21st chromosome.$\newline$This matches with III.$\newline \bullet$B. α-Thalassemia:$\newline$α-Thalassemia is associated with deletions or mutations on the 16th chromosome.$\newline$This matches with IV.$\newline \bullet$C. β-Thalassemia:$\newline$β-Thalassemia is associated with mutations on the 11th chromosome.$\newline$This matches with I.$\newline \bullet$D. Klinefelter's syndrome:$\newline$Klinefelter's syndrome is a result of an extra X chromosome, typically XXY.$\newline$This matches with II.$\newline$Now, let's match the items from List I with List II:$\newline A \rightarrow III, B \rightarrow IV, C \rightarrow I, D \rightarrow II \newline$This corresponds to Option 1.