Choose the correctly punctuated option:

The selection of the first option demonstrates correct punctuation by appropriately using a comma before the conjunction "and." In this case, the independent clauses "The dog ran fast" and "it barked loudly" are two complete thoughts that are closely related. The use of the comma indicates a natural pause and helps clarify the relationship between the two clauses, thus preventing any reader confusion about the structure of the sentence.

While the other options may contain grammatical elements that could lead to issues in clarity, the punctuation in the selected option ensures that the sentence flows smoothly and maintains proper grammatical structure. The comma creates a necessary distinction between the two independent clauses, reinforcing the coherence of the overall sentence.