On What Basis Was the The Federal Government Able to Claim

On what basis was the the federal government able to claim jurisdiction in the cases of the Americans convicted of child pornography?

A) The actions of those convicted crossed over international borders.
B) The actions of those convicted crossed over county borders.
C) The states were unaware of the criminal activities,so lost their claim of jurisdiction.
D) The federal government was concerned that the accused would not get a fair trial at the state level.