To solve this problem, we need to determine the sequence of genes on a linear chromosome based on the given recombination frequencies. Recombination frequency is directly proportional to the distance between genes on a chromosome. Let's analyze the given data:$\newline \bullet$Recombination frequency between a and c is 5%.$\newline \bullet$Recombination frequency between b and c is 15%.$\newline \bullet$Recombination frequency between b and d is 9%.$\newline \bullet$Recombination frequency between a and b is 20%.$\newline \bullet$Recombination frequency between c and d is 24%.$\newline \bullet$Recombination frequency between a and d is 29%.$\newline$Let's determine the sequence:$\newline \bullet$The smallest recombination frequency is between a and c (5%), suggesting they are closest.$\newline \bullet$The next smallest is between b and c (15%), indicating b is next to c.$\newline \bullet$The recombination frequency between b and d is 9%, suggesting d is next to b.$\newline \bullet$The recombination frequency between c and d is 24%, which is consistent with d being next to b.$\newline \bullet$The recombination frequency between a and b is 20%, which fits the sequence a, c, b.$\newline \bullet$Finally, the recombination frequency between a and d is 29%, confirming d is at the end.$\newline$Therefore, the sequence of genes on the chromosome is:$\newline$a, c, b, d$\newline$This corresponds to Option 4.