Liquid nitrogen is kept at a temperature of -320 degrees. When liquid nitrogen is heated it quickly boils and turns into a gas. Which pair of pictures represent the change caused by adding heat to liquid nitrogen?

So when something is boiling it is moving faster meaning the molecules are more spread out and not condense like a solid

So the answer is the 2nd set

c. because step up transformer steps up the input voltage i.e increases the input voltage  

the number of turns are greater on the secondary side of step up transformer  

transformer does not handle dc current