Complete the text with the correct parts of the sentences.

Extreme sports, also known as action sports or adventure sports, are thrilling activities that involve a high level of danger, speed, height, and physical exertion. With over forty different types of extreme sports, the definition of an extreme sport is ... . The term gained popularity in the 1990s, primarily due to its use by marketing companies to promote events like the X Games and the Extreme Sports Channel.
While the term "extreme sport" has become widely used to describe a variety of activities, there is ongoing debate about ... . Nonetheless, there are several common characteristics that are often associated with extreme sports. Firstly, these sports are typically associated with youth culture and tend to have a younger fan base. Secondly, extreme sports often involve a greater degree of solitude compared to traditional sports, ... . Lastly, many aspiring extreme athletes begin their journey without the guidance of a coach, although some may choose to hire one at a later stage.
Extreme sports, as categorized by the media, differ from traditional sports due to the increased presence of naturally uncontrollable variables. These variables, ... , including wind, snow, water, and mountains, inevitably impact the outcome of these activities.
Unlike traditional sporting events, where athletes compete against each other in controlled environments, extreme sports face challenges with maintaining constant conditions for all participants. While controlled events like the X Games can be organized, there are still environmental factors ... . Examples include fluctuating snow conditions for snowboarders, varying rock and ice quality for climbers, and unpredictable wave height and shape for surfers.