Ancient jewelry, pottery, and roads are examples of what? O Artifacts
O Archeology
O Auipu
O Aodex

Explanation:

An Artifact is an object made by a human being, typically an item of cultural or historical interest from the past, which in this case is Ancient meaning really old. All the others don't make sense.

The reason why the United States join the world war is described below in brief details.

Explanation:

The U.S. entered World War I because Germany began a violent venture. Germany sank many American merchant vessels around the British Sea which provoked the American entrance into the war. Another reason was Germany's violation of its commitment to reject permitted submarine battle in the Mediterranean and the North Atlantic, as well as its efforts to attract Mexico into an agreement against the United States, as his intentions for declaring war.