Clarification:
I believe that you're looking for what an experiment is, or how to make one, rather than its steps. If you were to look for its steps, the options would be different.
Elimination:
An experiment isn't a variable you'll change - A is incorrect.
An experiment isn't a set of lab rules - B is incorrect.
An experiment isn't the same thing as a research - D is incorrect.
An experiment is a procedure where you look for proof and evidence for your research. For this you will need to know how and what to do. - C is correct.
Hope it helped,
BiologiaMagister