The heat you feel from putting your hand near a fireplace conduction convention or radiation

The thermal radiation from the fire spreads out in all directions and is able to reach you. This thermal radiation is mostly in the form of infrared waves and visible light. In contrast, the campfire heat transferred via convection shoots straight up into the sky and never reaches you (i.e. hot air billows upwards).

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

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)