Why Were Mail Cars Connected to the Pullman Cars During

Why were mail cars connected to the Pullman cars during the Pullman strike?

A) The strikers wanted to create as big a disruption as possible.
B) So President Grover Cleveland could express his support for the union.
C) To justify federal intervention to end the strike by allowing railroad executives to claim the strike interfered with the mail.
D) To allow union leaders throughout the country to exchange correspondence during the strike.
E) To prevent anarchists from communicating with the strikers.