on one condition that

They will give us the money on one condition —that we pay it back within six months.

他们给我们提供资金有一个条件，即我们在六个月以内偿还。

《牛津词典》

In brief, we can conclude that the one-child policy, which has already generated many negative effects on the children's growth, is unsuitable for nowadays China's national condition.

简而言之，我们可以总结道，独生子女政策已经对儿童的成长产生许多消极的影响，它已经不适应与现代中国的国情了。

I will only do them on one condition, and that is I want to be able to teach you what the assumptions are that underlie the points in the derivation.

只在一个情况下我才会做，那就是要能够教会你们，假设是，构成了推导的基础。