A: Charge is invariant but mass is variant with velocity
B: Charge is conserved but mass alone may not be conserved
C: Repulsion is the sure test to know the presence of charge

Although mass will increase exponentially as a particle's velocity approaches the speed of light, charge is independent of velocity.

While attraction between an uncharged body and a charged body might happen owing to induction of charges from the charged body to the uncharged body, repulsion is regarded as the sure test to determine whether an item is charged or not. Repulsion, however, may only occur between two charged entities.