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You are conducting an experiment inside a train car that may move along level rail tracks. A load is hung from the ceiling on a string. The load is not swinging, and the string is observed to make a constant angle of 45 with the horizontal. No forces other than tension and gravity are acting on the load. Which of the following statements are correct? Check all that apply. [3 The train is an inertial frame of reference. C] The train is not an inertial frame of reference. C] The train may be instantaneously at rest. D The train may be moving at a constant speed in a straight line. D The train may be moving at a constant speed in a circle. C] The train must be speeding up. C] The train must be slowing down. C] The train must be accelerating