Jack-O-lanterns have always been made from hollowed out pumpkins

The correct statement about Jack-o-lanterns is:

False – Early “soulers” on Halloween night would bring hollowed-out turnips with candles inside.

Historically, before pumpkins became popular in the United States, people in Ireland and Scotland carved turnips or other vegetables to create lanterns for Halloween. Once pumpkins were introduced to the Halloween tradition in America, they became the preferred choice due to their size and ease of carving.

To address the other statements:

• False - Pumpkins are only used for Jack-o-lanterns in the United States: This is incorrect; while pumpkins are most commonly associated with Jack-o-lanterns in the U.S., other cultures have their own traditions of carving vegetables.
• True – Pumpkins are the only produce item that make for good jack-o-lanterns: This is misleading as, historically, turnips and other vegetables have also been used effectively.
• True – Pumpkins have always been a part of Halloween traditions: This is not true historically; pumpkins became popular for Jack-o-lanterns in the U.S. after Irish immigrants brought their traditions here, and they were not part of Halloween traditions historically in other cultures.

In summary, your best bet for "True" contexts revolving around Jack-o-lanterns primarily focused on pumpkins is in relation to American traditions specifically.