A union$$s $$secondary activity$$ is a:

a$.$ refusal to represent one of its members in a grievance against the employer because the member did not engage in a strike called by the union the previous year.

b$.$ recognized union$$s request for an injunction against an employer who refuses to bargain in good faith.

c$.$ union$$s picketing, in addition to a strike, of a company that is the target of the labor dispute.

d$.$ boycott or strike of an employer with whom a union has no labor dispute to persuade the employer to cease doing business with the company that is the target of the labor dispute.