Fortunately, however, ancient men made tools of stone, especially flint, because it is easier to shape than other kinds. (使用插入语)

相比之下，第二个句子会更加地道，因为地道的英语句子就是要写得跌宕起伏。

插入语可分以下几类：

短语插入语：generally speaking, to tell the truth, in a sense, in a word, strange to say

【例句】Parents, in a word, should never lose sight of the side-effects of computer games on their children.

【译文】总而言之，家长不该无视电脑游戏对小孩的副作用。

短句插入语：I suppose, as I see it, I believe, what is important

【例句】Environment, what is important, has a far-reaching influence on one’s personality.

【译文】重要的是，环境对人的性格有深远影响。

万能插入语：rather than肯前否后，这个短语可以放在句子中的任何一个成分后面。

【例句】It abolishes the presumption of innocence and places the citizen at the service of the state rather than the other way round.

【译文】新法废除了公民的无罪假定并且将公民置于为政府服务的地位，而非政府为公民服务。

一些相对特殊的插入语：在考研中有一些相对特殊的插入语具有较强的固定表达意味，例如：

to some extent 从一定程度上讲

at length 终于，最后;详细地

at the mercy of 在……支配下

以后的写作训练中，考生可以有意识地运用插入语，久而久之便会发现插入语的好处。