Question: The Bear is the second of the two operas by William Walton, the libretto was based on which play of the same title, by Anton Chekhov?

Context paragraphs:
The Boor (opera): The Boor is an opera in one act composed by Ulysses Kay to a libretto based on Anton Chekhov's comic play, "The Bear" (also known as "The Boor").  Kay wrote the libretto himself basing it on an English translation of the play by the composer Vladimir Ussachevsky.  The opera was commissioned by the Koussevitsky Foundation of the Library of Congress and is dedicated to the memory of Natalie and Serge Koussevitzky.  It premiered on 2 April 1968 in concert version at the University of Kentucky in Lexington, Kentucky.

The Bear (play): The Bear: A Joke in One Act, or The Boor (Russian: "Медведь: Шутка в одном действии" , "Medved': Shutka v odnom deystvii" , 1888), is a one-act comedic play written by Russian author Anton Chekhov.  The play was originally dedicated to Nikolai Nikolaevich Solovtsov, Chekhov's boyhood friend and director/actor who first played the character Smirnov.

The Bear (opera): The Bear is the second of the two operas by William Walton, described in publication as an "Extravaganza in One Act".  The libretto was written by Paul Dehn and Walton, based on the play of the same title by Anton Chekhov (which is also sometimes translated into English as "The Boor").

On the Harmful Effects of Tobacco: On the Harmful Effects of Tobacco (Russian: О вреде табака , "O vredye tabaka " ) is a one-act play written by Russian author Anton Chekhov; it has one character, Ivan Ivanovich Nyukhin.  First published in 1886, the play was revised by Chekhov and is best known from his 1902 version.  This was first published in English in "The Unknown Chekhov" (1954), a collection of writings.

The Cherry Orchard: The Cherry Orchard (Russian: "Вишнëвый сад" , "Vishnevyi sad " ) is the last play by Russian playwright Anton Chekhov.  Written in 1903, it was first published by "Znaniye" (Book Two, 1904), and came out as a separate edition later that year in Saint Petersburg, via A.F. Marks Publishers.  It opened at the Moscow Art Theatre on 17 January 1904 in a production directed by Konstantin Stanislavski.  Chekhov described the play as a comedy, with some elements of farce, though Stanislavski treated it as a tragedy.  Since its first production, directors have contended with its dual nature.  It is often identified as one of the three or four outstanding plays by Chekhov, along with "The Seagull", "Three Sisters", and "Uncle Vanya".

About Chekhov: About Chekhov (Russian: О Чехове , "O Chekhove " ) is a book of memoirs by a Nobel Prize-winning Russian author Ivan Bunin, devoted to Anton Chekhov, his friend and major influence.  Bunin started working on the book in the late 1940s in France.  It remained unfinished, was completed by the writer's widow Vera Muromtseva (aided by Leonid Zurov), and came out posthumously in New York City, in 1955.  Translated by Thomas Gaiton Marullo, the book was published in English in 2007, under the title "About Chekhov.  The Unfinished Symphony".

Sonya's Story: Sonya's Story (Russian: История Сони) is an opera by the British composer Neal Thornton to a libretto based on the original Russian text of Anton Chekhov's play "Uncle Vanya".  The libretto reproduces passages from "Uncle Vanya" in English translation with additional spoken text by Neal Thornton.  "Sonya's Story" premiered on 7 August 2010 at the Riverside Studios in Londonto celebrate Chekhov's 150th anniversary.  The production, part of the Tête à Tête festival was directed by Sally Burgess and designed by Charles Phu.

Troilus and Cressida (opera): Troilus and Cressida is the first of the two operas by William Walton.  The libretto was by Christopher Hassall, his own first opera libretto, based on Geoffrey Chaucer's poem "Troilus and Criseyde".  Walton dedicated the score to his wife, Susana.

Tatiana Repina: Tatiana Repina (Russian: Татьяна Репина ) — is a one-act drama play written by Russian writer Anton Chekhov in 1889.  It is a sequel of Alexey Suvorin's play "Tatiana Repina", with the same characters.  Chekhov's drama was dedicated to Suvorin.  Chekhov was friends with him and actively participated in the production of his "Tatyana Repina" play in Moscow.

Daughter of Albion Illegal: Daughter of Albion Illegal is a 1914 Russian film directed by Boris Glagolin and based on a story written by Anton Chekhov.  This was the second film adaptation of Chekhov's work.  The film was released ten years after his death; a time Chekhov thought no one would be reading his work anymore.  It is unknown if a copy of the film exists.

Supporting paragraphs: The Bear (opera) The Bear (play)
Answer: The Bear: A Joke in One Act