Section 9D. A county, except Worcester county, by vote of the county commissioners; a city having a Plan D or Plan E charter by majority vote of its city council, any other city by vote of its city council, approved by the mayor; a district, except as hereinafter provided, by vote of the registered voters of the district at a district meeting; a regional school district by vote of the regional district school committee; a veterans' services district by vote of the district board; a welfare district by vote of the district welfare committee; a district established under the provisions of section twenty-seven A of chapter one hundred and eleven by vote of the joint committee; may provide that it will pay one-half of the amount of the premium to be paid by the surviving spouse of an insured employee or a retired employee for hospital, surgical, medical, dental and other health insurance continued as provided in section nine B. A town shall provide for such payment either by a vote of the town, or by a majority of affirmative votes cast in answer to the following question which shall be printed upon the official ballot to be used at an election in said town:—''Shall the town pay one-half of the premium costs payable by the surviving spouse of an employee or retired employee for group general, or blanket hospital, surgical, medical, dental or other health insurance?''

Payment of the entire premium by the surviving spouse as required by section nine B shall not apply in any governmental unit which accepts the provisions of this section.