What is temperature in science, how fast molecules move or how cold or hot something is?

Temperature relates to the average kinetic energy of molecules (for a gas)

Temperature is the measure of Heat energy possessed by the substance.

also, when you touch something, it's not actually the "temperature" what makes you how hot the object is. it depends on its thermal conductivity. (search aerogel on YT)

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