The Bay City Rollers are a Scottish pop band whose popularity was highest in the mid 1970s.
 The "British Hit Singles & Albums" noted they were "tartan teen sensations from Edinburgh", and were "the first of many acts heralded as the 'biggest group since the Beatles' and one of the most screamed-at teeny-bopper acts of the 1970s".
 For a relatively brief, but fervent period (nicknamed "Rollermania"), they were worldwide teen idols.
 The group's line-up had numerous changes over the years, but the classic line-up during its heyday included; guitarists Eric Faulkner and Stuart John Wood, singer Les McKeown, bassist Alan Longmuir, and drummer Derek Longmuir.
Travis Aaron McNabb is a New Orleans-born and Nashville-based American drummer and percussionist.
 McNabb is perhaps best known as a longtime member of the band Better Than Ezra, although he has performed session and touring work with many acts during his career.
 Prior to joining Better Than Ezra in January 1996, McNabb toured with acts such as Vigilantes of Love, Beggars, and seminal Oregon-based punk rock band The Wipers.
 Since mid-2007, he has been the full-time touring drummer with Grammy-award winning Country/Bluegrass act Sugarland.
La Habanera is a 1937 German melodramatic feature film directed by Detlev Sierck (later Douglas Sirk).
 Zarah Leander, recently signed by UFA, is the main star in the lead role of Astrée Sternhjelm and performs its title song, "La Habanera".
 Like many of her films of this era, it proved an enormous box office success.
The Pleasantville Music Festival is a single-day music festival which takes place annually at Parkway Field in Pleasantville, New York.
 Some of the many acts that have performed at the Pleasantville Music Festival are: Guster, Gin Blossoms, Jakob Dylan, Joan Osborne, Marc Cohn, Big Head Todd & the Monsters, the English Beat, and Roger McGuinn.
 These major acts perform alongside up and coming national acts and small local bands from around the tri-state area.
Carmen (] ; ] ) is an opera in four acts by French composer Georges Bizet.
 The libretto was written by Henri Meilhac and Ludovic Halévy, based on a novella of the same title by Prosper Mérimée.
 The opera was first performed at the Opéra-Comique in Paris on 3 March 1875, where its breaking of conventions shocked and scandalized its first audiences.
Habanera is the popular name for "L'amour est un oiseau rebelle " ("Love is a rebellious bird"), one of the most famous arias from Georges Bizet's 1875 opera "Carmen".
 It is the entrance aria of the title character, a mezzo-soprano role, in scene 5 of the first act.
 It is based on a descending chromatic scale followed by variants of the same phrase in first the minor and then the major key, corresponding to the vicissitudes of love expressed in the lyrics.
 The vocal range covers D to F♯ with a tessitura from D to D.
Budgie are a Welsh hard rock band from Cardiff.
 They are described by author Garry Sharpe-Young as one of the earliest heavy metal bands and a seminal influence to many acts of that scene, with fast, heavy rock (an influence on the new wave of British heavy metal (NWOBHM) and acts such as Metallica) being played as early as 1971.
 The band has been noted as "among the heaviest metal of its day".
The Great Escape was a music festival held at Newington Armory, located within Sydney Olympic Park that took place in 2006 and 2007.
 Initially held over the Easter long weekend for the first two events, in 2008 it was announced the festival would take place on the Labour Day weekend, however the event was cancelled 2 months from the date due to poor ticket sales .
 It evolved from the 2005 Cockatoo Island Music Festival.
 The music and other attractions run over three full days (Good Friday to Easter Sunday in 2006–07), with some patrons camping from Thursday evening to Monday morning.
 Punters could attend either for the full weekend camping, purchase a 3-day pass and commute each day or attend a single day.
 Many acts also played the East Coast Blues & Roots Music Festival the same weekend, however The Great Escape line-up is more diverse featuring pop, hip hop, electronic and rock acts that would not fit into a Blues and Roots line-up.
 In addition to musical acts, there is also a wide range of other features such as comedy acts, bingo and trivia, conspiracy theory talks and yoga.
 There is no immediate future for the Great Escape at this point, but organisers are confident it will be resurrected in the near future.
Acid jazz, also known as club jazz, is a musical genre that combines elements of jazz, soul, funk, and disco.
 Acid jazz originated in the London club scene of the mid-1980s in the rare groove movement and spread to the US, Japan, Eastern Europe, and Brazil.
 Major acts included Brand New Heavies, Incognito, Us3, and Jamiroquai from the UK and Buckshot LeFonque and Digable Planets from the US.
 The rise of electronic club music in the mid to late 1990s led to a decline in interest, and in the twenty-first century, the movement became indistinct as a genre.
 Many acts that might have been defined as acid jazz are now seen as jazz-funk, neo soul, or jazz rap.
Steve Thompson (born 24 April 1952) is a British songwriter and record producer who is responsible for a number of single and album chart hits and well known songs recorded by international recording artists.
 He was instrumental in setting up the influential Neat Records.
 He was particularly active as a producer during (as well as being partially responsible for), the NWOBHM years (New Wave of British Heavy Metal) During this time he produced many acts and kick-started the careers of several influential heavy metal acts including the first recordings of Newcastle band Venom ( who are widely credited with the invention of black metal) and Raven who have been credited with being hugely influential by Metallica.

Question: How many acts are in the opera in which Habanera appears?
Answer: four