但随时钢琴弹得最好或者唱歌最好的呢？这个由你决定。

But who can play the piano the best or sing the most beautifully? That 'sup to you to decide.

youdao

中文可更好地表述如下：当决定性时刻来临时，要么由你来决定这个时刻，要么由这个时刻来决定你。

When a defining moment comes along, you define the moment, or the moment defines you.

youdao

由你自己来决定是否要认可这个品性、是否要将它表露出来并与世人分享。

It is up to you to choose this love and joy, bring it out of yourself and share it with the world.

youdao

And if you don't put a point but just put a number, this specifies the width of space that will be used by the number you're inserting there.

如果你不用点而只用数字，这个指定的长度是由,你插入的数字决定的。

哈佛公开课 - 计算机科学课程节选