Which of the following is an example of formal language? complaining ain’t gonna stop me from parking there. you can’t park there! the best solution to the problem is to require parking permits. all the kids should get themselves permission to park.

The answer is indeed "The best solution to the problem is to require parking permits."

Explanation:

Formal language is most commonly used when writing. It takes vocabulary and grammar into full consideration, following grammar rules and avoiding some lapses that are usual in spoken language. Formal language also tries to be more impersonal. In the sentence "The best solution to the problem is to require parking permits", the person who should or will find the solution is not mentioned. The speaker also avoids saying "in my opinion" or "to my mind", which helps to keep the impersonality of the tone.

The other sentences that were offered as options are characterized with informal qualities: the use of "ain't" and "gonna", the use of a reflexive pronoun - themselves - where it is not necessary and so on. Those are traits of spoken, and very informal, language.

no its not a run on sentence however i think you meant wet suits not sours also a run on sentence would be like surfers surf all winter long in southern california by using wet sours to keep them warm and the live their all year long  

we should all just get dogs.