It's uncertain ________ the experiment is worth doing. prefix="o" ns="urn:schemas-microsoft-com:office:office" ?xml:namespace> A. if prefix="o" ns="urn:schemas-microsoft-com:office:office"? ?xml:namespace> B. that C. whether D. how
【单选题】( )is a service which is based on polar orbiting satellites which receive and relay distress alerts from satellite EPIRBs and which provides their position