How are physical and chemical different

 A physical change in a substance doesn't change what the substance is. While a chemical change is where there is a chemical reaction, a new substance is formed and energy is either given off or absorbed.

There are many differences between physical and chemical change few points I discuss here.

A physical change occurs in a /elements /particles / molecules in which the molecules can be replaced each other but their inter construction will be the same.

So in the same way the chemical change are opposite to the physical change in this process the substance can transfer to a new substance in which contains different chemical composition it's mean two or more substance combine to form a new substance having same or different property combine by chemical reaction is known as Chemical change.

it is b that is the answer.