Why are backgrounds noises often included into radio programs

To provide context for the listener.

Explanation:

As per the question, the background noises and sounds to provide a context to the readers' that helps them relate to the content of the program and understand it effectively. As it is said, Context plays a vital role in readers' comprehensive understanding of a text as it not only assists them to read/go through between the lines(content) but also to know the author's purpose behind the creation of a particular work and the social and political scenario of the time it was written that aids the readers' to evaluate the text more accurately and effectively. Thus, option D is the correct answer.

your answer is c) experiments with water vapor showed that elements combine in specific proportions.