Protection of appurtenances of portable containers, skid tanks, and tanks for use as cargo tanks of more than __________ shall be protected from physical damage.

The correct answer, which states that the protection of appurtenances of portable containers, skid tanks, and tanks for use as cargo tanks of more than 1000 lbs water capacity shall be protected from physical damage, is significant as it underscores safety regulations in handling and storing propane.

In this context, the "water capacity" refers to the measurement of how much water can be held in the tank, which correlates to the tank's ability to safely hold propane. Tanks and containers of significant capacity, such as those exceeding 1000 lbs, pose a greater risk in terms of physical damage that could lead to leaks or ruptures, creating hazards.

Thus, regulations mandate that these larger tanks must have specific protective measures in place to minimize the risk of accidents due to physical damage from impacts or environmental factors. By setting this threshold at 1000 lbs, regulatory bodies aim to enhance safety protocols for handling larger quantities of propane, which are more likely to be involved in serious incidents if compromised. This regulation is intended to safeguard both people and property while handling propane in substantial amounts.