branch of economic theory

例句：

1. 1. The tree has several branches reaching towards the sky.
   这棵树有几条树枝伸向天空。
2. 2.The branch of science that studies the behavior of living organisms is called ethology.
   研究活体生物行为的科学分支被称为生态学。
3. 3. The scientist's research on the branch of medicine focused on the treatment of cancer.
   这位科学家对医学领域的分支——癌症治疗的研究。