For each blank in the following passage, there are four choices marked A, B, C and D. Choose the one that is most suitable and mark your answer by blackening the corresponding letter on the Answer Sheet. The first snowboards were made in the 1960s. However, it was in the late 70s that they became more__21__. Throughout the80s, more and more people began taking up the sport, even though snowboards were not allowed on most ski hills. __22__ its earlier problems, snowboarding is now the world’s __23__ growing winter sport and most resorts(度假地)welcome snowboards. In 1963, a Grade 8 student named Tom Sims __24__ a ski-board for a school project in New Jersey. Then, in 1966, a man name Sherman Poppen __25__ two skis together for his kids on Christmas day. He called his invention “ the Snurfer,” which __26__ the words “snow” and “surf”. In 1969, Jake Burton Carpenter received a __27__ for Christmas. He soon began designing boards, and today “Burton” is a popular __28__ of snowboard. By the 1980s, snowboarding had become very popular. __29__, most ski resorts did not allow snowboarding because they thought it was too __30__.Since many snowboarders were young, many older skiers did not want them on the ski hills. The snowboarders had to go to the backcountry, __31__patrolled（有巡逻的）resorts. Rejection at the resorts did not __32__ snowboarding from growing in popularity. Eventually, the owners of ski resorts changed their views. They __33__ that they could make more money by allowing snowboarding. One by one, the resorts __34__ to welcome snowboards. Today, many resorts even set __35__special areas where snowboarders can practice their creative tricks. 21.