This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
In the below organ, the pink colour material is formed predominantly of which of the following 
Select and explain. 
A. Thyroxine, B. Thyroglobulin, C. Monoiodotyrosine, D. Diiodotyrosine
B: Thyroglobulin
Answer: B: Thyroglobulin 
Explanation: The histology is that of thyroid gland. And the pink material is colloid. 
The thyroid gland stores iodide primarily as thyroglobulin.
The thyroid gland has a specialized active transport system that very efficiently traps iodide from circulating blood and can accumulate iodide against a large concentration gradient.
Within the thyroid, the iodide rapidly undergoes organification by which it is oxidized and covalently linked to tyrosine residues in thyroglobulin.
The iodinated tyrosine residues gradually become coupled to form thyroxine, the major secretion product of the thyroid.