3d网球：
Are you asking about 3D tennis video games or a type of tennis played in three dimensions? If it's the former, there are many great 3D tennis games available on various gaming platforms that offer a realistic and immersive experience. If it's the latter, I'm not sure if that's a thing, as tennis is typically played on a two-dimensional court. However, there are variations of tennis, such as beach tennis and paddle tennis, that are played on smaller courts and may involve more three-dimensional movement.
网球保发：
你好！ "网球保发" 是什么意思呢？我猜它可能是指在网球比赛中保住自己的发球局，不被对手破发。这在比赛中非常重要，因为如果你能够保住自己的发球局，你就可以继续领先并赢得比赛。你喜欢打网球吗？