Both slicing a tomato and a chemical change such as burning toast cannot be reversed however why is slicing a tomato still considered only a physical change

Both slicing a tomato and a chemical change such as burning toast cannot be reversed. Slicing a tomato still considered only a physical change because you are only altering the shape of the tomato by slicing. It does not change in color or produce bubbles when slicing.

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