英语语法分析

During the 1840s, Marx and Engels wrote a book together.

19世纪40年代期间，马克思和恩格斯一起写了一本书。

At the same time, his close friend, Engels, often wrote to praise him for his hard work in learning English.

与此同时，他的密友恩格斯经常写信表扬他努力学习英语。

Engels was an enigma.

恩格斯是一个迷。