It is, everyone agrees, a huge task that the child performs when he learn to speak, and the fact that he does so in so short a period of time challenges explanation.

Do the constantly changing fashions of women's clothes, one wonders, reflect basic qualities of inconstancy and instability?

It was probably not until the 1880's that man, with the help of more advanced steam locomotive, managed to reach a speed of one hundred mph (英里)

要点分析和参考译文

要点：“everyone agrees”为插入语。“and”连结两个并列句，前一句为“it is … that”强调句型;后一分句“the fact”后为同位语从句“that he does so in so short a period of time”，因此，后一分句的主要部分为the fact challenges(需要)explanation

参考译文：每个人都同意孩子学说话确实是件困难的事，并且孩子能在这么短的时间里做到的确需要很好的解释才行。

要点：“one wonders”为插入语，本句主干结构为“Do the fashions reflect qualities?”，“fashions” 有两个定语“constantly changing”和“of women's clothes”。“qualities”也有两个定语“basic”和“of inconstancy and instability”。

参考译文：我们不知道女性服装不断变化的时尚是否反映出不可靠和不稳定的基本特点。

要点：此句为强调句型“It was …that…”; that 从句中主语man和谓语managed 之间插入介词短语“with the help of …”作状语。