Which of the following statements best describes what is "relative" in the theory of relativity?
a. the theory says that everything is relative. b. the theory says that truth can never be established in any absolute sense. c. the theory says that measurements of motion make sense only when we state what they are measured relative to. d. the theory says that the speed of light is relative and depends on who is measuring it. e. the theory says that all scientific results must be considered within the context of the scientists' individual viewpoints.

Special relativity theory is based on the following two postulates:  

1. The laws of physics are the same in all inertial systems. There is no preferential system.  

2. The speed of light in vacuum has the same value for all inertial systems.  

Focusing on the first postulate, it can be affirmed that measurements of motion  make sense only when we state what they are measured relative to a reference system.

In addition, it deals with the dilation of time stating that time passes at different rates in regions of different gravitational potential. That is, the greater the local distortion of space-time due to gravity, the slower the time passes.  

b) phosphorus pentoxide