the Big Bang Theory the Conservation of Energy the Periodicity of Element Properties the Acceleration of Objects due to Gravity
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Which event or principle cannot have its validity directly tested by laboratory experiment?
Possibilities:
- the Big Bang Theory
- the Conservation of Energy
- the Periodicity of Element Properties
- the Acceleration of Objects due to Gravity

the Big Bang Theory