Cells in the thyroid have much higher concentrations of iodide ions than the extracellular fluid that surrounds them, which is delivered by the
blood. Are iodide ions transported into the thyroid cells by active transport or passive transport?
A active transport, because the cell must pump ions from regions of low concentration to high concentration
B. active transport, because charged ions cannot diffuse through the lipid bilayer of the cell membrane
C passive transport, because iodide ions diffuse into the cell from the surrounding fluids
D. passive transport, because charged ions are able to diffuse through the lipid bilayer of the cell membrane

A.

Explanation:

Passive transport is defined as the movement of ion and other molecules through cell membrane without any energy input while active transport is the movement of ions and other molecular substances across cell membranes with an energy input which allows, molecules to move from a region of lower concentration to a region of higher concentration.

Uptake of iodide ions by thyroid cell is an active transport which is mediated by sodium/iodide symporter (NIS) protein, found in  basolateral membrane of thyroid follicular cells. As the concentration of iodide ions is higher in thyroid cells, active transport make movement of  iodide ions form  extracellular fluid (lower concentration) to thyroids cells (higher concentration).

Hence, the correct option is A.

i think its the first one