Which of the following verifies a friction lighter’s function?

The function of a friction lighter is verified by its ability to produce a spark through the action of squeezing. This mechanism relies on the friction generated when components of the lighter are rubbed together, which in turn creates a spark sufficient to ignite a flammable material.

While the other options describe actions or utilities related to ignition sources, they do not directly illustrate how a friction lighter operates. For example, igniting flammable liquids or lighting rope fuses involves the outcome of the spark created by friction, but they do not define the lighter's functionality. Additionally, stating that a friction lighter requires an electrical charge is inaccurate, as this type of lighter operates solely based on mechanical action rather than any electrical mechanism. Therefore, the correct understanding of a friction lighter's function centers around its capability to create a spark through squeezing, which is foundational to its design and use.