BRUSSELS, Dec 20 (Reuters) - EU antitrust regulators have asked game developers and distributors if they think Microsoft (MSFT.O) will block their access to Activision Blizzard's (ATVI.O) games once it has bought the company, an EU document seen by Reuters shows."Please specify which partial exclusivity strategy or strategies you believe Microsoft would have the ability to deploy with respect to Activision Blizzard's console games after Microsoft's acquisition of Activision Blizzard," the questionnaire asked.The EU antitrust watchdog asked if such strategies would include degrading the quality or interoperability of Activision's games available on competing consoles or providing upgrades to Activision's games only on Xbox.Regulators asked what advantages and disadvantages game developers and publishers and console game distributors would face if a game is distributed exclusively on one console."Sony, as the industry leader, says it is worried about Call of Duty, but we’ve said we are committed to making the same game available on the same day on both Xbox and PlayStation."