Hypophosphatemia is manifested by an X-linked dominant allele. What proportion of the offsprings from a normal male and an affected heterozygous female will manifest the disease?

For an X-linked dominant disorder: affected female (X^A X^a) × normal male (X^a Y). Each child gets one X chromosome from the mother (either X^A or X^a, 50% probability) and either X^a or Y from the father. Daughters: 50% will be X^A X^a (affected), 50% will be X^a X^a (normal). Sons: 50% will be X^A Y (affected), 50% will be X^a Y (normal). Therefore, 50% of sons and 50% of daughters will manifest the disease. This matches option A. Option B would describe X-linked dominant inheritance from an affected father, while option C would describe Y-linked inheritance (which doesn't apply here).