杰克只有四岁。

Jack is only four years old.

youdao

尽管小杰克只有四岁，但他已经学会了自己做很多事情。

Little Jack has learned to do lots of things on his own, though he is only four years old.

youdao

在谷仓里，我发现了一面鼓。它之前是旧收音机上的部件，像一把吉他，但只有四根弦。

In the barn, I found a drum, which used to be part of an old tape-recorder. It's like a guitar, but it has four strings.

youdao

Because it takes three units where there's only four choices at each position to have at least 20 unique combinations.

因为每个位点上仅有四种可能性,只有采用三个碱基一组,才能取得至少二十种不同的组合方式

耶鲁公开课 - 生物医学工程探索课程节选

It's only got one of four possible choices at each position.

每个位点上都只有四种可能性

耶鲁公开课 - 生物医学工程探索课程节选

It runs about bearly four minutes so bear with me here.

它只有四分钟,你们再忍耐一下

耶鲁公开课 - 聆听音乐课程节选