None of the options is correct. Frog respires in three different manners; cutaneous or skin respiration; buccopharyngeal respiration; pulmonary or lung respiration. Lungs are poorly developed in frog, the inadequate supply of O2 obtained through lungs is supplemented through moist skin and buccal cavity. Hence, first statement is false. Heart of frog has three chambers, two atria and one ventricle. Hence, second statement is false. The frog excretes urea and thus is a ureotelic animal. The elimination of nitrogenous wastes is carried out by a well developed excretory system. The excretory system consists of a pair of kidneys, ureters, cloaca and urinary bladder. Frog do not change into uricotelic animal in any condition. Hence, third statement is false. In frog, fertilization is external and takes place in water. Within two weeks, fertilized eggs or zygotes develop into free-swimming aquatic larvae, called tadpoles, which undergo metamorphosis to become adult terrestrial frogs.