Which of the Following Actions of an Employer Would Be

Which of the following actions of an employer would be regarded as an unfair labor practice as per Section 8(a) of the National Labor Relations Act?

A) Using lockouts as defensive acts to protect businesses against sudden strikes and to prevent sabotage or violence
B) Discouraging membership in any labor organization by discrimination in regard to hiring or any other term of employment
C) Agreeing to bargain collectively with a duly certified representative of the employees
D) Firing employees for indulging in any unlawful activity at the workplace