Building up electric charges on a van de graaff generator is an example of static

Yes, that is true. Van de Graaff generators are devices that produce static electricity. Static does not involve acceleration, meaning it is motionless which applies to the building of electric charges since the building up of these electric charges are created in a way to not move. Therefore, the sentence you have stated is an accurate statement. 

Let me know if you need anything else. :)

               ~ Dotz

Yes, this is true. Van de Graaff generators are devices that produce static this electricity right now.

The correct choice is c