The correct answer is C) secure a line around a spar. A rolling hitch is a knot used to attach a line to a spar, pipe, or other cylindrical object. It provides a secure, non-slip connection that can be used to tie off lines or haul objects. This makes it particularly useful for securing lines around spars, such as on a sailboat. The other answer choices are incorrect because a rolling hitch is not typically used to make a temporary eye, mouse a hook, or shorten a line. Those tasks would require different types of knots or techniques.