Which of the following is an example of a type of load used in sling load operations?

In sling load operations, the correct example of a type of load is the M1151 HMMWV (Humvee). This military vehicle is designed for mobility, combat support, and transport in various operational environments. It is commonly utilized in sling load operations due to its robustness and adaptability.

The M1151 HMMWV can be securely rigged for transport under a helicopter, making it suitable for deploying forces and equipment in areas that are difficult to access by ground. This versatility is essential in military operations, particularly when rapid deployment is necessary.

Each of the other options represents loads that may also be used in different contexts but do not specifically capture the typical use scenario associated with sling load operations as effectively as the M1151. While standardized cargo crates and utility vehicle trailers can certainly be sling-loaded, the emphasis on tactical mobility and readiness is particularly exemplified by the choice of a military vehicle like the Humvee. A personnel carrier might be useful as a load but does not fit the specific operational paradigms as well as a combat vehicle used during missions. Thus, the M1151 HMMWV stands out as the most illustrative example of a load used in such operations.