Final answer:
An investigative report has a problem-solving function and is prepared voluntarily. It focuses on examining problems and suggesting solutions, characterized by critical thinking and strategic information organization. The correct answer is Investigative.
Step-by-step explanation:
The report type that has a problem-solving function and is prepared on a voluntary basis is the investigative report. These reports serve to examine a problem in detail and explain possible solutions. Unlike compliance or justification reports, which may be required by law or policy, or summary reports that condense information, an investigative report's purpose is to delve into a specific issue and underpin potential strategies for addressing it.
In the context of academic and professional settings, an investigative report might identify a problem, gather and analyze factual information about it, and ultimately draw conclusions or recommend actions based on the findings. This process often involves critical thinking and the strategic organization of information, reflecting reasoning strategies such as cause and effect, comparison and contrast, or problem and solution. Therefore, the correct answer to the student's question is a) Investigative.