Question
                         
                            Yellow-dog contracts:
                         
                            A. were used by employers to restrict union membership
                         
                            B. required membership in a labor ünion in order to work in certain trades
                         
                            C. enforced the idea of an open shop
                         
                            D. restricted the ability of a company to control its workers
                         
                            E. increased union membership by millions
                        
                    
                 
             
            
                
                    
                        
Answer
                        A. were used by employers to restrict union membership