4. a. 200 and 400 million years
b. 10 million years
c. CH4
d. 70
e. 350 F
f. 700 F
g. 1112 F
h. over 900 F
a. D
b. E
c. F
d. B
e. G
f. C
g. A
学习这篇文章对我来说比较困难。最根本的原因是词汇量不够翻译不通句子，不能理解文章的深层含义。花很多时间查找陌生的单词。通过阅读文章基本翻译后的文章，不仅了解了心理学的知识，开拓了不熟悉的领域，还认识了很多陌生的单词。
Learning this article is more difficult for me. The most fundamental reason is that the amount of words is not enough to translate sentences, can't understand the deep meaning of the article, and spend a lot of time looking up strange words. After the basic translation of the article through reading the article not only to understand the knowledge of psychology, opened up unfamiliar areas but also know a lot of strange words.
