Answer: A . to help the reader understand what economic resources are before introducing the three groups of economic resources.
Explanation:
Land, labor and capital are the three most important factors of production so in introducing factors of production first, the author wanted to give a background of what factors of production are before then giving the types of factors there are.
The background information given is to enable the reader understand what economic resources/ factors of production are so that they would then be able to understand the general need for land, labor and capital when they are introduced.