To solve this problem, we need to identify the condition associated with a broad palm and a single palm crease.$\newline \bullet$A single palm crease, also known as a simian line, is a single transverse crease that extends across the palm.$\newline \bullet$This feature is commonly associated with Down's syndrome, a genetic disorder caused by the presence of an extra chromosome 21.$\newline \bullet$Individuals with Down's syndrome often exhibit distinct physical characteristics, including a broad palm with a single palm crease.$\newline$Let's evaluate the options:$\newline \bullet$Option 1: Down's syndrome - This is the correct association as it is known for the presence of a single palm crease.$\newline \bullet$Option 2: Turner's syndrome - This condition is characterized by the absence of one X chromosome in females and does not typically involve a single palm crease.$\newline \bullet$Option 3: Klinefelter's syndrome - This condition involves an extra X chromosome in males and does not typically involve a single palm crease.$\newline \bullet$Option 4: Thalassemia - This is a blood disorder and does not involve a single palm crease.$\newline$Therefore, the correct answer is Option 1: Down's syndrome.