Final answer:
The F1 sharks' genotype, given that they are blue with angled fins and resulted from a cross between true-breeding blue angled fin sharks and true-breeding white straight fin sharks, is Rrff.
Step-by-step explanation:
The question relates to genetics and the inheritance of traits in sharks, where the traits are shark color and fin shape.
The correct genotype of the F1 offspring is option b) Rrff. This is because the offspring show the blue color and angled fins, which means they must have inherited the dominant blue color allele (R) and the dominant angled fin shape allele (F) from the blue shark parent. However, since they are true-breeding, the white shark with straight fins must have the recessive alleles, resulting in a genotype of rrff for that parent. The F1 offspring, therefore, would have one dominant and one recessive allele for color (Rr) and two recessive alleles for fin shape (ff) since fin shape was not expressed in the phenotype of the F1 generation.