您好！可以改为定语从句：Outdoor Film Festival which/that was held in December, is the first festival in Asia that focuses on cycling mountain bike documentaries and environmental protection movies.第一个定语从句：Outdoor Film Festival which/that was held in December，先行词是Festival，后面缺主语，用指物的关系代词which/that引导定语从句，代替先行词fesitival，并且在定语从句中充当主语。 ...
Outdoor Film Festival,held in December,is the first festival in Asia which focuses on cycling mountain bike documentaries and environmental protection movie...
