Final answer:
The best subheading for the paragraph would be 'Carolina quake hit North Florida'.
Step-by-step explanation:
The best subheading for this paragraph would be b. Carolina quake hit North Florida. This subheading accurately reflects the main idea of the paragraph, which discusses the impact of the famous Charleston, South Carolina, shock on northern Florida. The passage describes how the shock was felt in various towns along the east coast of Florida, including St. Augustine and Jacksonville, and mentions the strong aftershocks that were felt in the following months.