Tadpoles Must Undergo a Major Metamorphosis to Become Frogs

Tadpoles must undergo a major metamorphosis to become frogs. This change includes reabsorption of the tail, growth of limbs, calcification of the skeleton, increase in rhodopsin in the eye, development of lungs, change in hemoglobin structure, and reformation of the gut from the long gut of an herbivore to the short gut of a carnivore. Amazingly, all of these changes are induced by triiodothyronine. What is the most likely explanation for such a wide array of effects of thyroxine?

A) There are many different forms of triiodothyronine, each specific to a different tissue.
B) Different tissues have triiodothyronine receptors that activate different signal transduction pathways.
C) Some tissues have membrane receptors for triiodothyronine, while other tissues have triiodothyronine receptors within the nucleus.
D) Different releasing hormones release triiodothyronine to different tissues.