Answer the following question: Information:  - BMX, an abbreviation for bicycle motocross, is a cycle sport performed on BMX bikes, either in competitive BMX racing or freestyle BMX, or else in general on- or off-road recreation. BMX began when young cyclists appropriated motocross tracks for fun, racing and stunts, eventually evolving specialized BMX bikes and competitions.  - BMX racing is a type of off-road bicycle racing. The format of BMX was derived from motocross racing. BMX bicycle races are sprint races on purpose-built off-road single-lap race tracks. The track usually consists of a starting gate for up to eight racers, a groomed, serpentine, dirt race course made of various jumps and rollers and a finish line. The course is usually flat, about wide and has large banked corners that help the riders maintain speed.  The sport of BMX racing is facilitated by a number of regional and international sanctioning bodies. They provide rules for sanctioning the conduct of the flying, specify age group and skill-level classifications among the racers, and maintain some kind of points-accumulation system over the racing season. The sport is very family oriented and largely participant-driven, with riders ranging in age from 2 to 70, and over. Professional ranks exist for both men and women, where the age ranges from 18 to 40 years old.  - The 2009 UCI BMX World Championships took place at the Adelaide Showgrounds in Adelaide in Australia and crowned world champions in the cycling discipline of BMX .  - Cycle sport is competitive physical activity using bicycles. There are several categories of bicycle racing including road bicycle racing, time trialling, cyclo-cross, mountain bike racing, track cycling, BMX, and cycle speedway. Non-racing cycling sports include artistic cycling, cycle polo, freestyle BMX and mountain bike trials. The Union Cycliste Internationale (UCI) is the world governing body for cycling and international competitive cycling events. The International Human Powered Vehicle Association is the governing body for human-powered vehicles that imposes far fewer restrictions on their design than does the UCI. The UltraMarathon Cycling Association is the governing body for many ultra-distance cycling races.  - A BMX bike is an off-road sport bicycle used for racing and stunt riding. BMX means bicycle motocross.  - Cycling, also called bicycling or biking, is the use of bicycles for transport, recreation, exercise or sport. Persons engaged in cycling are referred to as "cyclists", "bikers", or less commonly, as "bicyclists". Apart from two-wheeled bicycles, "cycling" also includes the riding of unicycles, tricycles, quadracycles, recumbent and similar human-powered vehicles (HPVs).  - A unicycle is a vehicle that touches the ground with only one wheel. The most common variation has a frame with a saddle, and has a pedal-driven direct drive. Unicycling is practiced professionally in circuses, by street performers, and in festivals and as a hobby. Unicycles have also been used to create new sports such as unicycle hockey. In recent years unicycles have also been used in activities similar to mountain biking or trials.  - UCI BMX World Championships are the world championships for BMX racing (bicycle motorcross) held under the regulations of the Union Cycliste Internationale (UCI), the sport's international governing body.  - The Union Cycliste Internationale, commonly known by the acronym UCI, is the world governing body for sports cycling and oversees international competitive cycling events. The UCI is based in Aigle, Switzerland.  - Motocross is a form of off-road motorcycle racing held on enclosed off-road circuits. The sport evolved from motorcycle trials competitions held in the United Kingdom.  - Freestyle BMX is bicycle motocross stunt riding on BMX bikes. It is an extreme sport descended from BMX racing that consists of five disciplines: street, park, vert, trails, and flatland.    What object entity has the relation of 'sport' with the subject '2009 uci bmx world championships'?   Choices: - bicycle motocross  - cycle sport  - cycling  - hockey  - motocross  - motorcycle racing  - mountain biking  - polo  - road bicycle racing  - sport
Answer:
bicycle motocross