credible, convincing, probable, verisimilar, arguable, likely, presumed, believable, presumptive, equiprobable, more...

implausible, unlikely, unbelievable, inconceivable, improbable

plausibly, implausible, implausibly, more...

least, most, such, sound, first, several, whole, only, best, prima, implausible

safe to say,   easy to believe,   worth considering,   easy to accept,   seems right,   likely to be true,   seems true,   sounds right,   this is possible,   colorable basis