Initiating blood clot is the main function of platelets.
If sodium ions are outside of a cell, they will tend to move into the cell based on both their concentration gradient and the voltage across the membrane (the more negative charge on the inside of the membrane). So cells pump out the extra ions.
This is what my candidate teacher said..
Answer:
B. Gametophytes of seedless vascular plants
Not sure why that's an interesting one maybe it's a good thing to look it up on Google or something