According to the text What is the Central idea?​

The main idea, sometimes referred to as the central idea, is the most important thought of a text.

The central idea (main idea) in a piece of writing is the point that the author wants you to remember most. Some writers may state the main idea, but it is often implied, which means the reader has to make inferences (what the text says + what I know) about it.

c. government control over the unsettled western lands