Definition: Compose a new way to ask the same question. The new question must be asking the exact same thing as the original question does. Without any other information, you should be able to tell that the original question and the new question are the same. Preserve bracketed phrases in your new question. You can change the rest of the question provided the above requirements are satisfied. The new question must have a natural, fluent formulation, as if it were composed by a native English speaker. You will be given three pieces of information to help you create better questions. Those are: "Answer": the answer to the question, e.g., "Honolulu". "Answer Type": the type of the answer, e.g., "Location". "Auxiliary Information" is a detailed description of some concepts mentioned in the question, if any.
Input: original question: How many librettists are there for the [Carmen] opera?
answer: 2
answer type: Librettist.
auxiliary information: Carmen is an opera in four acts by the French composer Georges Bizet. The libretto was written by Henri Meilhac and Ludovic Hal√©vy, based on a novella of the same title by Prosper M√©rim√©e. The opera was first performed at the Op√©ra-Comique in Paris, on 3 March 1875, and at first was not particularly successful. Its initial run extended to 36 performances, before the conclusion of which Bizet died suddenly, and thus knew nothing of the opera's later celebrity. The opera, written in the genre of op√©ra comique with musical numbers separated by dialogue, tells the story of the downfall of Don Jos√©, a na√Øve soldier who is seduced by the wiles of the fiery Gypsy, Carmen. Jos√© abandons his childhood sweetheart and deserts from his military duties, yet loses Carmen's love to the glamorous toreador Escamillo, after which Jos√© kills her in a jealous rage. The depictions of proletarian life, immorality and lawlessness, and the tragic death of the main character on stage, broke new ground in French opera and were highly controversial. After the premiere, most reviews were critical, and the French public was generally indifferent.

the [Carmen] opera contains how many librettists?