Select every form that can fill the gap: "The guide has ____ us the whole collection."

Explication

Two of these fill the participle slot after has. Shown is the ordinary British participle and the safer choice in formal prose, while showed doubles as a participle in American English, where the guide has showed us the collection is recorded as standard. Showing needs a form of be in front of it, and showen is not an English word at all.