a labor union is an organization of workers who

Question

a. hold exactly the same political beliefs
b. represent the interests of the business community
c. work in the same job or industry
d. work on farms.

i think its b

Answer 1

I think they want you to say c.
Generally it is the management, not the laborers, who claim to represent the interests of the business community.
This homework of yours seems to have some of its own built in bias.

Answer 2

A Labor Union represents the working members of a particular industry. For instance the "Screen Writers Guild" is a labor union representing the writers, not the owners of the movie companies. So C would be the better answer