Falcon-Hunter Chess (also called Schultz's Chess, One-Way Chess, or Meso Chess) is a chess variant invented by Karl Schultz in 1943 employing the two fairy chess pieces falcon and hunter.
 The game takes several forms, including variations Hunter Chess and Decimal Falcon-Hunter Chess added in the 1950s.
Capablanca Random Chess (CRC) is a chess variant invented by Reinhard Scharnagl in 2004.
 It combines the piece set and 10×8 board from Capablanca Chess with the permutation idea of Fischer Random Chess (FRC or Chess960).
 This game won a contest in 2005 held at "The Chess Variant Pages" to design a variant based upon the theme of the number 10.
Diplomat chess is a chess variant invented by Carlos Martín-Fuertes in 2003 as a contribution to a Contest to design a chess variant on 43 squares, organised by "The Chess Variant Pages".
 It is played on a circular board with 43 cells, including the center circle which is considered orthogonal "and" diagonal to every adjacent cell.
 The game includes a fairy piece called 'diplomat' which instead of capturing can suborn enemy pieces.
Marseillais chess (also called Double-Move chess) is a chess variant in which each player moves twice per turn.
 The rules of the game were first published in Marseillais local newspaper "Le Soleil" in 1925.
 This chess variant became quite popular in the late 1930s with such chess grandmasters as Alexander Alekhine, Richard Réti, Eugene Znosko-Borovsky, and André Chéron playing it.
Penultima is a game of inductive logic, played on a chess board.
 It was invented by Michael Greene and Adam Chalcraft in Cambridge in 1994.
 The game is derived from the chess variant Ultima (otherwise known as "Baroque Chess"), and played with a standard chess board and pieces, each piece having different movement and capture rules from standard chess.
 In a manner similar to the game Mao, which was a popular game in Cambridge at that time, the rules for each piece vary from game to game, and are initially kept secret from the players.
 Penultima is similar in style to Eleusis, Zendo and Mao.
 The name of the game is a pun on "penultimate", and "Ultima", the name of the chess variant.
Way of the Knight (WOTN) is a chess variant invented by Ralph Betza before 1994.
 It was an attempt to create a chess variant which had attributes of both standard chess and role-playing games.
Ouk-Khmer (also known as Cambodian Chess) is a chess variant which D. B. Pritchard claimed was played in Cambodia although its actual origins appear to be unknown.
 Pritchard gives the source as P. A. Hill.
 It combines elements of makruk and xiangqi.
 Similar to xiangqi, it is played on the intersections of an 8×8 monotone board (Instead of 8x9).
 Contrary to Pritchard's claim, the actual variety of chess played in Cambodia today, known as "Ok" or "Ouk Chatrang" is nearly identical to Makruk.
 The authenticity of the game described by Pritchard remains doubtful.
Congo is a chess variant invented by Demian Freeling in 1982 when he was nearly eight years old.
 His father (Dutch abstract games designer Christian Freeling) encouraged him to design a variant using a 7×7 gameboard.
 Demian was already familiar with chess and xiangqi, and the result blends some features from both.
 Congo became the second-most popular chess variant at the Fanaat games club in Enschede, the Netherlands.
Ubongo is a board game developed by Polish-born Swedish game designer Grzegorz Rejchtman.
 It originally appeared as "Pyramidens Portar" by the Swedish publisher Kärnan and won the Swedish "Årets spel" prize in 2003.
 The game was later released in Germany in 2005 as "Ubongo" by the publisher Kosmos and got 4th place at the German board game competition and was among the finalists in the International Gamers Award.
The British Chess Variants Society (or BCVS) was an association of chess variant players and developers active between 1997 and 2010.
 The Society took over publication of "Variant Chess", a chess variant magazine which had been published since 1990; the magazine ceased publication with the dissolution of the Society.

Question: Which game is a chess variant, Ubongo or Ouk-Khmer?
Answer: Ouk-Khmer