A mass m attached to a spring of constant k is oscillating on a frictionless surface. A second mass m is dropped on top of the first at the moment the spring is extended to the end (x - a) Which of the following is true? Explain why A) The maximum velocity does not change. B) The amplitude of oscillation A decreases. C) The frequency of oscilations f does not change. D) The frecuency of escilations. f increases E) The geriod of oscillation increases