Define central or main idea.
a. a summary of a piece of writing
b. a one-on-one or small group question-and-answer session
c. the thesis statement of original documents
d. an object created by someone with firsthand experience

The right answer is C.

It is considered that the idea is the first of the acts of comprehension while being limited to the simple knowledge of something. An idea, therefore, is a mental image of an object or rational knowledge generated by the natural conditions of understanding.

The notion of central, moreover, admits many uses. It can be the space where coordinated actions converge and what is basic or essential to something.

The central idea is therefore the most important content of a work, a proposal, a project, etc. Without this central idea, the work would not be understood or it would lose its value.

Examples: "The central idea of Little Red Riding Hood is that one should not disobey his parents"

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