Which process is an example of a chemical change? a. cooking a steak
b. chopping a tree
c. heating a cup of tea
d. drying clothes in the dryer

A is the closest thing. You change the composition of the steak. You don't in any of the others.

Explanation:

Usually when you cook something, you are doing something to the composition of the object being cooked. A steak might not be obvious, but boiling an egg should be.

Chopping a tree is something physical. You are removing mass in such a way that the tree will fall. There's nothing chemical about that.

Heating a cup of tea looks like it might be chemical. After all steam is sometimes given off which looks like it is chemical. It's not. The water in the tea is just changing phase.

Drying clothes in a dryer. Again, this looks like something might have changed. After all the mass of the clothes just became less. But all you are doing is separating two masses (leaving one of them behind).

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