Changing an include file will affect all the pages that link to it such as a navigation bar. Suppose you want certain pages to display a certain navigation bar not available on other pages. Which is the BEST method to do this?

Option C is the best approach because it maintains the single source of truth benefit of includes while handling variations intelligently. The include file can detect the current page type or context and dynamically output the appropriate navigation menu. Writing separate include files (Option A) creates maintenance overhead, while abandoning includes (Option B) defeats the purpose of code reuse and makes future changes more difficult.