Playing computer games 主语.
is very interesting. 系表.
这是个简单句,只能有一个谓语
所以主语中的play就只能用分词形式了.
Playing computer games 是个整体.
computer games ARE very interesting.
BUT: Playing computer games IS very interesting.
注意这两句的区别.
前面的主语是复数的.
后面的主语是单数的.
'玩游戏'这一动作,是抽象的,通常用单数.