A positive pulse is sent along a spring. A short time later, a negative pulse with a smaller amplitude returns. Assuming there are no frictional losses, which of the following statements could account for this observation? Question 6 options: a) There is not enough information to answer the question. b) The other end of the spring is unattached ( ie it is a free-end) c) The spring is attached to a second spring of a higher density and slower speed. d) The other end of the spring is attached to a fixed-end. e) The spring is attached to a second spring of lower density and faster speed