Nowdays many young people have great i______ in palying computer games.

如你没看错,答案给错了.interest（兴趣）不可数.例如：
He began to have interest in political affairs.他开始对政治感兴趣了.但是不也有个短语是have an interest in吗？你记错了。show /take an interest in 对……表现出兴趣