Why Was Johnson Picked as Lincoln's Running Mate in 1864

Multiple Choice

Why was Johnson picked as Lincoln's running mate in 1864?

A) They were both lifelong Republicans.
B) They held remarkably identical political positions.
C) They agreed on the need for strict terms to readmit southern states into the Union.
D) As a gesture of unity, they combined to create a National Union ticket.
E) Johnson and Lincoln had already served together in the Illinois state government.