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。
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。
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。
The problem affects metropolitan areas of all sizes, but big ones-the country's economic engines-are in the worst shape.
大中小型城市皆受此问题困扰，但尤以作为国家经济引擎的大型城市为甚。
In this course, students, parents, teachers and even our society are all outside reasons which make it possible for some of the students to become problem ones.
在这个过程中，学生、家长、教师和社会环境都是因变量，在学生成长的不同阶段成为“问题学生”产生的诱因。
All strings in this problem (both encrypted and decrypted ones) will consist of only uppercase English letters (' a '-' Z ').
问题中的所有字符串(编码与解码字符串都是)只包含大写英文字母('A '- 'Z ')。
All strings in this problem (both encrypted and decrypted ones) will consist of only uppercase English letters (' a '-' Z ').
问题中的所有字符串(编码与解码字符串都是)只包含大写英文字母('A '- 'Z ')。
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