1. Consider the following images from a manufacturer's promotional materials for ISES they offer. Notice there are MANY different ISEs available. Note typical limits of detection and dynamic ranges. Also notice that for each, a "Construction" is briefly described. This is a major characteristic of ISEs. Some like pH meters are glass-walled. Others are a crystalline material, some are liquid like with organic ionophores present. Which choice best explains why this is the case? a) The different materials only reflect products from different manufacturers to avoid patent infringement. b) ion selective electrodes rely on differential and selective binding of an ion at a surface or interface. The ISE surface must be a material capable of selective binding of the analyte ion. c) glass can always be used for all ions, but the thin glass membranes are difficult to prepare for many manufacturers. d) none of these answers explain