challenge

a demanding or stimulating situation; "they reacted irrationally to the challenge of Russian power"

a call to engage in a contest or fight

questioning a statement and demanding an explanation; "his challenge of the assumption that Japan is still our enemy"

a formal objection to the selection of a particular person as a juror

a demand by a sentry for a password or identification

take exception to; "She challenged his claims"

issue a challenge to; "Fischer challenged Spassky to a match"

ask for identification; "The illegal immigrant was challenged by the border guard"

raise a formal objection in a court of law