Correct Option: D

Cystic fibrosis: It is a common disorder of caucasian race in which thick and more salty mucus blocks the respiratory tract. The homozygous recessive condition produces the defective protein which regulates chloride transport channel. Cretinism: In this disorder the physical growth, mental growth and sexual growth in children is retarded. Such a dwarf and sterile child is called a cretin. It is due to hyposecretion of thyroid hormones. Thalassemia: Due to defective production of α or β chains of haemoglobin, autosomal recessive. Haemophilia: Sex linked disorder due to defective recessive gene.