Answer:
The correct answer is b. X-linked dominant.
Step-by-step explanation:
In X- linked dominant disease the disease is linked with the X chromosome which shows its effect in the phenotype when transferred from the affected parent. Bob is affected by this X- linked dominant skin disease which means he will transfer this disease to all his daughters because in daughter one X chromosome comes from father and one from mother.
Therefore all girls will have X- linked dominant trait of skin disease and will show the same skin condition as bob but all males would be normal as the Y chromosome will be transferred to them from father and normal X chromosome will come from mother.