ensure
verb (also insure especially in North American English)
ɪnˈʃʊə(r) ɪnˈʃɔː(r) 
ɪnˈʃʊr to make sure that something happens or is definite
ensure something The book ensured his success.ensure somebody something Victory ensured them a place in the final.ensure (that)… Please ensure (that) all lights are switched off.