Answer:
The correct answer is letter "B": government agencies advertisements.
Explanation:
Public sources of information feed secondary market research which looks for obtaining valuable data from different pools of information without contributing to the gathering of the information directly. Usually, the information is provided by sources coming from government agencies or some of its extensions such as public libraries. Public sources of information are distributed in magazines, trade publications, newspapers or newsletters.
Thus, government agencies' advertisements fall under this category.
