Which of the following is a crucial step when preparing to cross a fence?

Engaging the safety is a crucial step when preparing to cross a fence because it ensures that the firearm is secure and cannot accidentally discharge while you are navigating the obstacle. Safety mechanisms on firearms are designed to prevent accidental firing, which is especially important in potentially hazardous situations such as crossing a fence where you may have to maneuver your body and the firearm in close quarters. By engaging the safety, you significantly reduce the risk of an unintentional discharge that could be dangerous to yourself or others.

The other options do not directly contribute to safety during this specific action. For instance, firing a warning shot is generally discouraged as it can pose a risk to others and is not a practical measure when crossing a fence. Taking off your gloves may not have any impact on firearm safety, and checking the time does not relate to the immediate concern of securing your firearm while crossing a fence.