Infertility is a public health problem that affects all societies, not least traditional ones such as the Maasai of east Africa.

不孕症是个公共卫生问题，影响到所有社会，尤其是传统的社会群落，如东非的马赛部族。

youdao

But if I give them all really hard problems, they don't get the chance to develop the good problem-solving habits that they'll get with the easy ones.

但是，如果我给他们的都是非常难的问题，那么他们就没有机会来养成良好的解决问题的习惯。

youdao

One problem is that, although the four 1949 conventions have been signed by all countries, support for the tougher 1977 ones still lags.

其中一个原因就是虽然所有的国家都签署了1949年通过的四个公约，许多国家却拖延签署规则更加严格的1977年的附加议定书。

youdao