【单选题】He is believed ______college exam, for he is now studying very hard now.
【简答题】All his investments have been (succee+d)______ and he is believed to be extremely rich.
【单选题】有压管道的管径D与管流水力半径的比值D/R=( )
【单选题】He is believed _______ the college exam, for he is now studying xery hard.