单项选择题

Making snow angels usually falls under the category of children’s winter recreation, but in early 2007, the process took on a whole new meaning. Almost 9,000 people gathered on the state Capitol grounds in Bismarck, North Dakota, to set a new world’s record for the most people making snow angels at one time. They were determined to break Michigan’s record of 3,784. Participants ranged from families with children to snowplow drivers. One woman was there to mark her 99th birthday! Kids of all ages flapped their arms in the snow and a young baby even made a snow angel by having her car seat spun in circles.
In the context in which it appears, "mark" most nearly means （）

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