What type of error is found in this sentence: "Sometimes the difference between being a good firefighter and an average firefighter comes down to weather or not the firefighter is properly trained?"

The identified error in the sentence pertains to a misuse of a word that sounds similar but has a different meaning. In this context, the correct expression should be "whether or not" instead of "weather or not." The word "weather" refers to atmospheric conditions, while "whether" introduces alternative conditions or choices. This distinction is crucial for conveying the intended meaning of the sentence regarding the qualifications of a firefighter.

The other options do not apply here because there are no grammatical issues that need to be addressed regarding subject-verb agreement or tense, punctuation is properly utilized, and the sentence structure is clear and coherent. The only correction needed relates to using the appropriate word to accurately express the intended idea.