Which of the following sentences has incorrect punctuation?

The chosen sentence contains incorrect punctuation because it improperly connects two independent clauses without a coordinating conjunction or proper punctuation. Independent clauses can stand alone as complete sentences, and when they are joined, they generally require a conjunction (like "and" or "but") before them or should be separated by a semicolon or a period to form distinct sentences.

In this case, "We saw the movie" and "the acting was great" are both independent clauses. The lack of a coordinating conjunction or appropriate punctuation creates a comma splice, which is a grammatical error. To correct this, the sentence could be rewritten as either "We saw the movie, and the acting was great" or "We saw the movie; the acting was great."