The bridge player's frequent errors, although frustrating for his partner, were _____ his defeat, since none of the competing players could determine, from the cards he played, what cards he likely held - a necessary prerequisite to figuring out how to block his plays. 
Choices: an insurance against      , the reason for, an indication of     , an obstacle to    , a hurdle for   , the guarantee of
Answers: an obstacle to    , a hurdle for