Which of the following is an example of a simple machine?

A lever is indeed an example of a simple machine because it consists of a rigid bar that pivots around a fixed point called a fulcrum. It allows heavy loads to be lifted with less effort by redistributing the force applied. This mechanism operates under the principle of mechanical advantage, enabling users to amplify their input force to perform tasks more efficiently.

In contrast, the other options do not fit the definition of simple machines. An engine is a complex machine that converts energy into mechanical work, a battery stores electrical energy and does not perform mechanical work directly, and a transistor is an electronic component used to control the flow of electrical current, which fundamentally differs from the mechanics of simple machines. Simple machines, such as levers, wheels and axles, pulleys, inclined planes, screws, and wedges, serve as the building blocks for understanding more complex machines, exemplifying fundamental principles of mechanics.