melting iron ore. producing lumber. molding plastic. crushing rock into gravel.
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Use the information below to answer the question. Manufacturing uses many steps to change natural resources into products. Some of these steps change natural resources into industrial materials. These steps are called primary processes. All of the following are primary processes except
Possibilities:
- melting iron ore.
- producing lumber.
- molding plastic.
- crushing rock into gravel.

molding plastic.