Which of the following is an example of a second-class lever?

A second-class lever is characterized by having the load located between the effort and the fulcrum. In the case of a wheelbarrow, the wheel acts as the fulcrum, the load is placed in the bucket of the wheelbarrow, and the effort is applied at the handles when lifting the load. This configuration allows the user to lift heavier loads with less effort, as the effort arm (distance from the fulcrum to the point where you apply force) is longer than the load arm (distance from the fulcrum to the load).

In contrast, scissors and tweezers function as third-class levers, where the effort is applied between the load and the fulcrum, making them less efficient for lifting heavy loads. A fishing rod operates differently as it's primarily used to exert force to cast and retrieve, not to lift a load in a way that defines a second-class lever. Hence, the wheelbarrow is a clear illustration of the mechanics of a second-class lever.