Final answer:
True, vaults are designed to be airtight and water tight, while grave liners do not provide such sealing and are primarily intended to support the casket without sealing features.
Step-by-step explanation:
The statement is true: vaults are often sealed and designed to be airtight and water tight, whereas grave liners are not intended to seal in the same way and typically do not offer the same level of protection. Vaults are designed to protect the integrity of the casket and maintain the grave space by preventing the ground from settling. On the other hand, grave liners serve a basic function of supporting the casket, but they do not offer the same sealing features as a vault. Therefore, in the context of funeral goods and services, it's important to clearly disclose these differences to consumers.