Concept:Islamic marriage law outlines who is permissible and who is prohibited as a spouse.Close blood relatives such as sisters are permanently forbidden in marriage.Explanation:A Muslim man may marry a divorced woman, so option A is not the correct exception.A friend's daughter and a cousin are not forbidden; they fall outside the prohibited degrees.However, a blood sister is a mahram and is permanently unmarriageable in Islam.This prohibition is clearly stated in the Qur'an, which forbids marriage to one's sisters.Answer:The correct option is B. blood sister.