WordNet sense 1 (march in protest; take part in a demonstration):

march

WordNet sense 2 (show or demonstrate something to an interested audience):

demo, exhibit, present, show

WordNet sense 3 (provide evidence for; stand as proof of; show by one's behavior, attitude, or external attributes):

attest, certify, evidence, manifest

WordNet sense 4 (establish the validity of something, as by an example, explanation or experiment):

prove, shew, establish