Hyper-Tech Enterprises manufactures mechanical parts used in air conditioning and heating units. The company employs over 300 workers at its Alabama facility. None of the Hyper-Tech employees belong to a union; however, management believes that unionization is in the near future. A representative of a local union has recently visited Hyper-Tech in an attempt to solicit members and have them sign authorization cards. Enough eligible employees have signed authorization cards to petition the NLRB for an election. Hyper-Tech's top executives are considering fighting the unionization efforts. Which of the following, if true, suggests Hyper-Tech has engaged in an unfair labor practice? a. Hyper-Tech managers prohibited union representatives from soliciting employees who were on duty.
b. Hyper-Tech managers intervened when pro-union employees solicited other employees while both were on duty.
c. Hyper-Tech managers barred nonemployee union representatives from entering the firm's building.
d. Hyper-Tech managers prohibited distribution of union literature in the company cafeteria.