Which one of the following examples of corporate behavior would most clearly represent a violation of the Sherman Act?

A) A retailer offers quantity discounts to large institutional buyers.

B) The members of a labor union meet and agree not to work for a specific firm unless the starting wage is at least $10 per hour.

C) Two firms that are in different, unrelated industries merge.

D) Two firms in the same industry agree in a telephone conversation to submit identical bids on a government contract.