Properties of iron, barium, and phosphorus. explain why nails are made of iron but they are never made of barium or phosphorus.

Nails are made up of iron not of phosphorus and barium.  

As both phosphorous and barium are relatively weaker than iron ,phosphorus breaks easily and barium is also fairly weak. Iron nails are already also not that strong, but their weight and strength are sufficient.  

So the nails are made up of iron.

d: the voltage of the secondary coil is less than that of the primary coil.

im not suree sorry if wrong

why is arctic sea ice important? arctic sea ice keeps the polar regions cool and moderate global climate. sea ice has a bright surface; 80 percent of the sunlight that strikes it is reflected back into space. as sea ice melts in the summer, it exposes the dark ocean surface.