Which of the Following Statements Is True of Primary Picketing

Which of the following statements is true of primary picketing?

A) It is expressed directly to the employer with whom the picketers have a dispute.
B) It is protected by the National Labor Relations Act,even if it is for an unlawful purpose.
C) It does not have constitutional or statutory protection.
D) It does not constitute an unfair labor practice,even if the picketers are violent or coercive.