So sometimes they go down hills, and then sometimes they go across flat land, then down hills, etc.

所以有时选手从山上滑下来，然后有时他们穿过平地，然后再下山，等等。

" Cross-country skiing, " we've already explained, is skiing across flat land using your arms and your legs in a very different way than if you go downhill skiing.

“越野滑雪” ，我们已经解释过了，它是用你的胳膊和腿在平坦的土地上滑雪， 其方式与下坡滑雪的方式截然不同。