A Scrum Master is introducing Scrum to a new Team.

According to the Scrum Guide, the action that the Scrum Master should take when the Team decides that a Sprint Retrospective is unnecessary is to begin facilitating productive and useful Sprint Retrospectives. The Sprint Retrospective is an essential event for the Scrum Team to inspect itself and create a plan for improvements to be enacted during the next Sprint. The Scrum Master is responsible for ensuring that this event takes place and that positive outcomes are achieved. The other options are not valid actions, as they either imply that the Scrum Master complies with or ignores the decision of the Team (such as complying with it, calling a meeting with senior management, or consulting with the Product Owner), which is not consistent with Scrum values and principles.