Question: Ocean's Kingdom is a ballet choreographed by a Danish Danseur who since 1990 has bore what?
Context: Les Noces is a ballet choreographed by Jerome Robbins, subsequently New York City Ballet balletmaster, to the 1923 version of Stravinsky's eponymous music for American Ballet Theatre with sets by Oliver Smith under the supervision of Rosaria Sinisi, costumes by Patricia Zipprodt, and lighting by Jennifer Tipton.  The premiere took place March 30, 1965, at the New York State Theater, Lincoln Center.  The choreographer re-staged "Les Noces" for New York City Ballet to a recording of the piece by the Pokrovsky Ensemble, sung in the full-throated style of traditional Russian village wedding celebrations.  The restaging premiered May 20, 1998, again at the New York State Theater.  It was Robbins' last work. Ocean's Kingdom is a ballet choreographed by Peter Martins on New York City Ballet to eponymous music and libretto by Paul McCartney.  The work's premiere took place on Thursday, 22 September 2011, at the Fall Gala in the David H. Koch Theater, Lincoln Center. Scènes de ballet is a one-act ballet choreographed by Frederick Ashton, who created it during 1947–48 to Igor Stravinsky's eponymous music from 1944.  The first performance was given by the Sadler's Wells Ballet, at the Royal Opera House, London. Ballo della Regina is a one-act ballet choreographed by George Balanchine to music by Giuseppe Verdi.  It is a set of variations set to ballet music (titled "La Peregrina") that Verdi cut from Act 3 of the original 1867 version of his opera "Don Carlos".  Its premiere performance was on 12 January 1978, by the New York City Ballet at New York State Theater in Lincoln Center. Flore et Zéphire is a one-act ballet choreographed by Charles-Louis Didelot to music by Cesare Bossi, premiered in London at the King's Theatre, Haymarket on Thursday, 7 July 1796.  The ballet tells the story of Zephyr, the fickle west wind, and his wife Flora, a nymph of flowers and springtime.  The ballet was originally composed in 1795 for performance in Lyon, France, and was revised in 1796 prior to its London premiere.  "Flore et Zéphire" used "flying machines" to send dancers soaring above the stage on nearly invisible wires, in order to enhance the presentation of Flora and Zephyr as spirits of the air.  The ballet is credited with the introduction of dancing "en pointe" to the stage. El sombrero de tres picos ("The Three-Cornered Hat" or "Le tricorne") is a ballet choreographed by Léonide Massine to music by Manuel de Falla, commissioned by Sergei Diaghilev and premiered complete in 1919.  It is not only a ballet with Spanish setting but one that also employs the techniques of Spanish dance (adapted and somewhat simplified) instead of classical ballet. Études is a one-act ballet choreographed by Danish dancer and choreographer Harald Lander to piano studies by Carl Czerny arranged for orchestra by Knudåge Riisager.  It is considered Lander's most famous choreographic work and brought him international fame.  The work premiered on 15 January 1948 at the Royal Theatre in Copenhagen with the Royal Danish Ballet, with scenery and costumes by Rolf Gerard and lighting by Nananne Porcher. Peter Martins (born 27 October 1946) is a Danish danseur and choreographer.  He was a principal dancer with the Royal Danish Ballet and with the New York City Ballet (NYCB), where he joined George Balanchine, Jerome Robbins and John Taras as balletmaster in 1981, retired from dancing in 1983 at which time he became Co-Ballet Master-In-Chief with Robbins, and since 1990 has borne sole responsibility for artistic leadership of City Ballet. Tschaikovsky Pas de Deux is a ballet choreographed by George Balanchine to a composition by Pyotr Ilyich Tchaikovsky originally intended for act 3 of "Swan Lake" (op. 20, 1875-1876).  With costumes by Barbara Karinska and lighting by Jack Owen Brown, it was first presented by New York City Ballet at the City Center of Music and Drama, New York, on 29 March 1960.  Robert Irving conducted the New York City Ballet Orchestra.  The dancers were Violette Verdy and Conrad Ludlow. A Midsummer Night's Dream is a two-act ballet choreographed by George Balanchine to Felix Mendelssohn's music to Shakespeare's play of the same name.  In addition to the incidental music, Balanchine incorporated other Mendelssohn works into the ballet, including the Overtures to "Athalie", "Son and Stranger", and "The Fair Melusine", the "String Symphony No. 9 in C minor" and "The First Walpurgis Night".  "A Midsummer Night's Dream", Balanchine's first completely original full-length ballet, premiered at New York City Ballet on 17 January 1962, with Edward Villella in the role of Oberon, Melissa Hayden in the role of Titania, and Arthur Mitchell in the role of Puck.  The ballet employs a large children's corps de ballet.  Act I tells Shakespeare's familiar story of lovers and fairies while Act II presents a strictly classical dance wedding celebration.  The ballet dispenses with Shakespeare's play-within-a-play finale.  "A Midsummer Night's Dream" opened The New York City Ballet's first season at the New York State Theater in April, 1964.
Answer: sole responsibility for artistic leadership of City Ballet