The question requires completion with an idiomatic phrase to describe the experience of filling out different forms for a driving license. Let's examine the options:
Therefore, the idiom "a pain in the neck" accurately completes the sentence: "The different forms to fill for a driving license are a pain in the neck."
In conclusion, "a pain in the neck" is the correct choice because it conveys the nuisance associated with filling out multiple forms for a driving license.