b. intracellular fluid moves to the outside of cells
Explanation:
The presence of an excess of sodium ions in the extracellular fluid would make it hypertonic with respect to the intracellular fluid. The concentration gradient would drive the intracellular fluid towards the outside of the cell to balance the concentration of the fluids on either side. The passive movement of fluids occurs across the cells and is driven by the concentration gradient only. The biological membranes are permeable for fluid movement such as the movement of water across it.
You can infer that the birds once had a common ancestor but became separated. Mutations in copying their genes stacked and caused changes in the beaks so the birds could be more well off or better adapted in their new environment.
