Seawater Is Rich in Iodine and Is Found in Coastal

Seawater is rich in iodine and is found in coastal soils and in seafood. This might explain why scientists observer that ________.

A) goiters rarely appear in people living near the coast
B) fish have body fluids that are isotonic to seawater
C) hormones generally travel through the blood circulatory system
D) many sea creatures have shells composed of calcium