Answer: A. It is the specific idea the passage focuses on that is the best choice that defines the thesis of a passage.
Step-by-step explanation:
A thesis is a statement that the passage intends to prove. It is the main idea of a passage that guides and directs the entire content of the writing. It is usually found in the introduction or conclusion of the passage, and it aims to summarize the key points and arguments of the author.
Therefore, option A is the correct definition of a thesis statement.