A deficiency in the diet of the element Iodine [I] can lead to goiter. This is why in the U.S. we placed more of it in all table salt ("iodized salt").
The membrane structures that function in active transport are proteins and lipids. Proteins function in active transport as pumps.
"Exponential growth" means that the bigger it is, the faster it grows.
That's Choice 'D'.
