The group of sentences that best demonstrates sentence fluency is B. That is, your answer would be the following: "Instead of going to the school dance, I had to stay home because I broke my curfew. I had to miss the school carnival as well. Hopefully I will learn my lesson this time".
This is the case because the writer has chosen well-built constructions by using linking words to join sentences and sentence parts. For instance, the adverbs "instead" and "hopefully". They create semantic relationships between the sentences and therefore make the whole writing piece more fluently.