Which of the Following Examples Illustrates Preemption as Mentioned in the U.S.Constitution?​

Which of the following examples illustrates preemption as mentioned in the U.S.Constitution?​ 

A)  The central government of Podjun vesting the entire duty of charting, implementing, and executing welfare policies to its local governments​ 
B) The central government in Frosbern giving its state governments more power and discretion over welfare programs 
C) The states of Girublia and Bokwost signing an interstate agreement to protect forest reserves that fall in shared boundary 
D) The state of Hulton withdrawing itself from the federal union of Jengren foreseeing potential conflicts with the federal government 
E) The central legislative body of Korolumbia deciding to make collection of taxes the exclusive right of the national government