Select the most appropriate answer from the list of options given in (a), (b), (c) or (d) for each question. 1. with respect to controlling fluids in pipework, the function of a butterfly valve is to: (a) regulate the flow rate of fluid through a pipe but has a non-linear flow response. (b) prevent reverse flow of fluid through a pipe. (c) completely stop fluid flow between two points in a pipe due to their linear flow response.. (d) throttle the flow of fluid through a pipe and have an approximately linear flow response between opening angles of between 45° and 90°.