they were doubtful that the cord would hold|it was doubtful whether she would be admitted|dubious about agreeing to go
dubious :open to doubt or suspicion
the candidate's doubtful past|he has a dubious record indeed|what one found uncertain the other found dubious or downright false|it was more than dubitable whether the friend was as influential as she thought
dubious :not convinced
they admitted the force of my argument but remained dubious