A:比赛开始了。Bǐsài kāishǐ le。 B:加油!加油!中国加油!Jiāyóu!jiāyóu!Zhōnɡɡuó jiāyóu! Now do you have some sence with how to use Jiayou? Good luck! 加油!
You can find the answer in my blog. The grammar of Chinese corner.