Answer: B
Analysis:
Jason zài yóuyǒng bǐsài zhōng gěi Kombi fàngshuǐ le.
Jason 在 游泳 比赛 中 给 Kombi 放水 了。
Jason deliberately lost to Kombi in the swimming competition.
“放水 (fàngshuǐ)” means “to deliberately lose a game” in this sentence. So B is the correct answer.