'Overt' means open to view, public, not hidden or secret. 'Obvious' means easily understood or evident, which is similar but not identical to overt. Looking more closely, none of the options are truly good synonyms. 'Odiferous' means smelly, 'odious' means hateful, 'ovation' is applause, 'overpower' means to overcome. Only 'obvious' is somewhat close in meaning.