Once a year,a race is held for old cars.这里为什么不是By 而是for?

Once a year,a race is held for old cars.这里为什么不是By 而是for? 冠词的选用Once a year,a race is held for old cars.这里为什么不是the race 英语翻译Once a year,a race is held for old cars.A lot of cars en Once a year,a race is held for old cars.是个什么结构? 新概念英语2册56课once a year,a race is held for old cars. old car r A Festival for the Dead is held once a year in Japan.中的is he 英语翻译A festival for the Dead is held once a year in Japan.Thi A festival for the Deal is held once a year in Japan.这 关于动词使用请问 The race is held once a year.这样的比赛一年举办一次. Once a year we show our love for our fathers by celebrating( Wanted,Aan English teacher for a ten-year-old boy 这里的wanted Here _______(be) a letter for you.这里be为什么是is 还有为什么不是have